Solid-state image pick-up device of the charge-coupled device type synchronizing drive signals for a full-frame read-out

ABSTRACT

A solid-state CCD image pick-up device includes optoelectric transducing elements corresponding to pixels vertically and horizontally arrayed in a matrix forming column linear arrays defining a column direction and at least one vertical charge transfer path associated with a corresponding adjacent column linear array. Pixel signals are vertically transferred from the column linear arrays to the vertical charge transfer paths such that gate signals occurring at predetermined times are applied to gate electrodes of the vertical charge transfer paths to permit the pixel signals to be scan read by a horizontal charge transfer path. Switching elements are provided for transfer gate electrodes and a drive circuit sequentially generates drive signals for groups of gate electrodes during periods in which the switching elements are rendered conductive to allow a full frame scan read to be performed by supplying a predetermined number of timing signals to the gate electrodes. The pick-up device can be fabricated with high density integration and high pixel density and can be provided with an improved vertical overflow drain structure. The image pick-up device also provides an electronic shutter function having improved vertical resolution. A shift register for producing improved vertical resolution is also disclosed.

This is a divisional of application No. 08/169,769 filed Dec. 20, 1993,U.S. Pat. No. 3,410,349 which is a continuation of application No.07/725,105 filed Jul. 3, 1991, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates generally to a solid-state image pick-updevice of the charge-coupled device (CCD) type. More specifically, thepresent invention relates to solid-state image pick-up devices which maybe fabricated with high density integration and high pixel density.According to one aspect of the present invention, a solid-state imagepick-up device is provided with an improved vertical overflow drainstructure. According to another aspect of the present invention, asolid-state image pick-up device provides an electronic shutter functionhaving improved vertical resolution. In particular, the presentinvention employs a shift register for producing improved verticalresolution. The present invention is particularly advantageous forsolid-state image pick-up devices providing functions for photographinga motion picture in an interlace scan read mode and photographing astill picture in a noninterlace/frame scan read mode.

BACKGROUND OF THE INVENTION

Solid-state image pick-up devices of the interline transfer type areused for electronic cameras, copying machines, and other video devices.In this type of image pick-up device, a plurality of photodiodes, eachdefining a pixel, are vertically and horizontally arrayed in a matrix.Vertical charge transfer paths are disposed between adjacent lineararrays of photodiodes, which extend in the column or vertical direction.A horizontal charge transfer path is disposed at one end of the verticalcharge transfer paths. The area of the device where the photodiodes andthe vertical charge transfer paths are formed is called thephotodetecting area. Light shield layers for shielding light incident onthe surfaces of the vertical and horizontal charge transfer paths arenormally provided on these surfaces.

FIG. 1 is a plan view showing a selected portion of the photodetectingarea A, shown in FIG. 3. A plurality of n⁺ impurity layers are arrayedin a matrix and are buried in a P-well layer, which is formed in thesurface region of a semiconductor substrate, to form a plurality ofphotodiodes, e.g., photodiodes Pd₁ and Pd₂. Vertical charge transferpaths such as paths L₁, L₂ and L₃, which are formed between adjacentcolumns of the matrix of the photodiodes Pd₁ and Pd₂, are provided fortransferring signal charges in the direction of arrow Y. The other areaof the device than the photodetecting area including those photodiodesand the vertical charge transfer paths, forms the channel stop area. Aplurality of gate electrodes G₁ -G₄, for example, which are made ofpolycrystalline silicon layers, are formed on the surfaces of thevertical charge transfer paths L₁, L₂ and L₃. The image pick-up deviceprovides a four-phase drive system based on each quartet of gateelectrodes, which receive clock signals φ₁, φ₂, φ₃, and φ₄.

As shown in FIG. 1, a photodiode Pd₁ is formed from the two parallelgate electrodes G₁ and G₂, and the photodiode Pd₂ is formed from the twoparallel gate electrodes G₃ and G₄. The same structure iscorrespondingly applied for the remaining photodiodes and gateelectrodes (not shown). The photodiodes Pd₁ and Pd₂ are connected viatransfer gates Tg₁ and Tg₂, respectively, to the vertical chargetransfer paths L₁, L₂ and L₃. The clock signals φ₁ -φ₄, which are set ata predetermined high voltage, permit the charge from the photodiodes tobe transferred to the vertical charge transfer paths.

With voltage variations of the clock signals φ₁, φ₂, φ₃, and φ₄according to the four-phase drive system, potential wells and potentialbarriers are sequentially generated at predetermined times t₀ to t₄, asshown in FIG. 2. The vertical charge transfer paths L₁, L₂ and L₃transfer signal charges in the direction Y toward the horizontal chargetransfer path (see FIG. 3). The horizontal charge transfer pathtransfers the signal charges from the respective vertical chargetransfer paths at predetermined times so that the signal charges areread out sequentially.

The solid-state CCD image pick-up device thus arranged provides aso-called interlace/two-field scan read system for reading the signalcharges. In the read system, odd-numbered groups, i.e., linear arrays ofphotodiodes, define an odd-numbered field, and even-numbered groupsdefine an even-numbered field. The signal charges generated in theodd-numbered field are first read out of the photodiodes and then thesignal charges of the even-numbered field are read out. Consequently,the signal charges for one frame are read out. However, whenphotographing a still picture using the conventional image pick-updevice, because the even-numbered field and the odd-numbered field arecombined to form one frame of an image, the time difference between thefields deteriorates the quality of the image.

FIG. 3 illustrates a solid-state image pick-up device of the frametransfer type (FT-CCD), which provides a scan read function based on theaccordion transfer system. See Theuwissen, A. J. P. et al., "TheAccordion Imager, A New Solid-State Image Sensor," PHILIPS TECHNICALREVIEW VOL. 43, No. 1/2, 1986. This solid-state image pick-up devicewill be described with reference to FIGS. 3 through 9.

As shown in FIG. 3, the device is made up of a photodetecting portion Aconsisting of a number m of vertical transfer paths L_(l) to L_(m)providing optoelectric transducing and charge transfer functions, astorage portion B consisting of charge transfer paths, which is disposedadjoining the vertical charge transfer paths L_(l) to L_(m), and ahorizontal charge transfer path C, which is coupled to one end of thegroup of the charge transfer paths in the storage portion B. Portions Band C generally have surfaces which are covered with a light shieldfilm. Transfer gate electrodes, extending in the charge transferdirection Y, are disposed side by side on the upper surfaces of thevertical charge transfer paths L_(l) to L_(m) in a manner such that thegate electrodes correspond to the pixels.

Gate signals are applied to the gate electrodes at times characteristicof the accordion transfer system. In an exposure mode, potential wellsand potential barriers corresponding to the pixels are generated in thevertical charge transfer paths L_(l) to L_(m). In a transfer mode, thesignal charges are transferred in the Y direction by varying thepotential wells and the potential barriers at predetermined times. Thegate signals are generated in such a way that a shift register, denotedas D, shifts a start pulse IM in synchronism with clock signals φ₁ andφ₂. Gate electrodes are likewise provided for the charge transfer pathsin the storage portion B. The signal charges are transferred in the Ydirection by gate signals generated in such a way that a shift registerE transfers a start pulse ST in synchronism with clock signals φ₁ andφ₂.

The vertical charge transfer paths L_(l) to L_(m) and the chargetransfer paths in the storage portion B synchronously transfer pixelsignals generated in the photodetecting portion A to the storage portionB, where the pixel signals are temporarily stored. Then, the pixelsignals are transferred line by line from the storage portion B to thehorizontal charge transfer path C. Every time the horizontal chargetransfer path C receives the pixel signal, it horizontally transfers thepixel signal in synchronism with a gate signal generated by a shiftregister F (not shown). In this way, all of the pixel signals are readout.

The timing of the related signals for the scan read operation areillustrated in FIGS. 4(a) through 4(c). As shown in FIG. 4(a), the startpulses IM and ST are supplied to the shift registers D and E. Thosestart pulses are transferred in synchronism with the two-phase clocksignals φ₁ and φ₂. Then, as shown in FIG. 4(b), gate signals A₁, B₁, C₁,. . . , and H₁, which are derived from the bit output contacts of theshift register D, are sequentially supplied to the gate electrodes ofthe vertical charge transfer paths L_(l) to L_(m) in photodetecting areaA. Similarly, as shown in FIG. 4(c), gate signals A_(s), B_(s), C_(s), .. . , H_(s), which are derived from the bit output contacts of the shiftregister E, are sequentially supplied to the gate electrodes of thecharge transfer paths in the storage portion B. For simplicity, only thegate signals corresponding to eight gate electrodes are illustrated.

When the voltage of the gate signals A₁, B₁, C₁, . . . , H₁ and A_(s),B_(s), C_(s), . . . , H_(s) is varied, the potential wells and thepotential barriers, as shown in FIG. 5, are progressively changed sothat the pixels signals are transferred, in order from pixel signalsq_(s) closest to the horizontal charge transfer path C, to the chargetransfer paths under the gate electrodes in the photodetecting area Aand the storage portion B (the even-numbered gate electrodes and theodd-numbered gate electrodes being denoted Ev and Od, respectively).

The charge transfer through a vertical charge transfer path and thecharge transfer path adjacent to the former in the storage portion B canbest be understood by referring to FIG. 6. Assuming that the exposuretakes place at time t₀, potential wells (marked as hatched squares) andpotential barriers (white squares) are alternately generated, accordingto a layout of the gate electrodes, in the vertical charge transferpaths in the photodetecting area A. Pixel signals q_(a), q_(b), q_(c),and q_(d) are generated along with the potential wells of pixels. Thepixel signals are progressively transferred to portion B, starting fromthe pixel signal qa closest to portion B. The generation of thepotential wells and the potential barriers resembles the gradualexpansion and contraction of the bellows of an accordion, hence thereason for referring to the charge transfer system under discussion asthe accordion transfer system.

After all of the pixel signals have been temporarily stored in thestorage portion B, the pixel signals are transferred in the accordiontransfer mode and time sequentially read out through the horizontalcharge transfer path C.

The solid-state image pick-up device based on this scan read system isadvantageous in that a minimal number of transfer gate electrodes arerequired, which is favorable for high density integration.

In the image pick-up device just described, the shift register circuitryis constructed with CMOS transistors, and this circuitry, thephotodetecting area A, the storage portion B, and the horizontal chargetransfer path C are all fabricated into a semiconductor substrate.

The shift register is arranged as shown in FIG. 7 while a longitudinalsectional view of it in the semiconductor substrate is shown in FIG. 8.In FIG. 7, the shift register is constructed between power sourcevoltages Vcc and VDD (VCC>V_(DD)). The bit stages of the shift registerare constructed with inverting circuits each consisting of a p-channelMOS transistor connected to the power source Vcc and an n-channel MOStransistor. Both transistors are complimentarily coupled with oneanother. AMOS transistor, which is made conductive and nonconductive byclock signals φ₁ and φ₂, is connected between the input and outputcontacts. In FIG. 7, capacitive elements ε are constructed utilizinginterline capacitance. If the start pulse IM (or ST) is applied to thefirst bit stage, the shift register shifts the start signal insynchronism with the clock signal φ₁ and φ₂, and produces gate signalsat the bit output contacts in synchronism with the clock signal φ₁ andφ₂.

When the shift register and the charge transfer paths are fabricatedinto a single semiconductor chip, the structure is as shown in FIG. 8.For example, a plurality of n-type impurity layers are formed in theregion to serve as a photodetecting area in the p-type semiconductorsubstrate so as to form the vertical charge transfer paths L_(l) toL_(m). A gate oxide film (not shown) is formed on the upper surfaces ofthe vertical charge transfer paths L_(l) to L_(m), and gate electrodesare layered on that oxide film. An n-Well layer is buried in a driveregion where the circuitry of the shift register is to be formed. A pairof p⁺ -type impurity layers are provided in the n-well layer. Gateelectrodes η_(p) are layered with a gate oxide film, not shown, to forma p-channel MOS transistor. An n⁺ -type impurity layer is buried in thesemiconductor substrate (p-Sub), and gate electrodes η_(n) are formed onthe surface to form an n-channel MOS transistor. Those gates η_(p) andη_(n), and predetermined nodes are connected to form the CMOS invertingcircuit (see FIG. 8).

In the solid-state image pick-up device of the CCD type thusconstructed, the power source voltage Vcc is set at approximately 10 Vand another power source voltage V_(DD) is set at 0 V. The gate signalvoltage at the gate electrode also varies between 0 V and 10 V.

In the solid-state image pick-up device, the peripheral circuitry,including the shift registers controlling charge transfer, isconstructed of CMOS transistors. Accordingly, it is extremely difficultto provide the image pick-up device with improved functions such as aso-called overflow drain, which drains unnecessary or excessive chargesto the semiconductor substrate. In addition, it is difficult toimplement an electronic shutter function. These difficulties are due toboth the structure of the device and breakdown voltage.

With respect to the structural limitations, the conventional imagepick-up device is based on the frame transfer type in which the verticalcharge transfer paths include the mechanism for producing pixel signals.If the electronic shutter function is introduced into the image pick-updevice, the smear component of the pixel signals is inevitably increasedin the resultant reproduced picture. Therefore, the introduction of theelectronic shutter function into the conventional image pick-up deviceis impractical.

With respect to the breakdown voltage limitation, if the verticaloverflow drain function is introduced into the conventional imagepick-up device, high voltage in the range of about 15 to 25 V must beapplied to the semiconductor substrate. This voltage range is highenough to potentially destroy the impurity regions corresponding to thenodes of the CMOS transistors and to cause the gate oxide films to breakdown.

If the electronic shutter function is realized in the conventional imagepick-up device, a much higher voltage must be applied to thesemiconductor substrate than in the case of introducing the verticaloverflow drain.

These problems can best be understood by referring to FIG. 9, whichshows additional details of the conventional image pick-up device. Tointroduce the electronic shutter function into the image pick-up device,an interline transfer system is necessarily used for the chargetransfer. In the photodetecting area, a plurality of n⁺ -type impuritylayers are arrayed in matrix in a p-well layer buried in an n-typesemiconductor substrate (n-Sub), thereby to form photodiodes. Aplurality of n-type impurity layers, which serve as the vertical chargetransfer paths L_(l) to L_(m), are formed adjoining the n⁺ -typeimpurity layers. Further, p-type impurity layers are buried around them,and gate electrodes are layered, to form channel stoppers.

In a drive region, a p-well layer is buried, and a pair of n⁺ -typeimpurity layers are formed in the p-well. A gate oxide film layer (notshown) is layered thereon, and a gate electrode η_(n) is layered on theoxide film layer to form an n-channel MOS transistor. A p⁺ -typeimpurity layer is buried in the semiconductor substrate (n-Sub), a gateelectrode η_(p) is formed on the surface to form a p-channel MOStransistor. A CMOS inverting circuit for the shift register shown inFIG. 7 is formed by properly connecting gate electrodes η_(n) and η_(p)and predetermined nodes.

To provide the structure of the so-called vertical overflow drain, avoltage in the range of 15 to 25 V is applied to the semiconductorsubstrate. To also provide the electronic shutter function, a structureis required so that, when a shutter voltage SS is applied to the p-welllayer in the photodetecting area, which drains the charges generated bythe photodiodes to the semiconductor substrate, an npn transistor isformed between the photodiode and the substrate to allow the charge toflow to the substrate.

To transfer the pixel signals, which are generated in the photodiodes byexposure to light, to the vertical charge transfer paths, a high voltageof approximately 12 V is applied to the transfer gates. To provide thenormal charge transfer operation by the vertical charge transfer paths,the voltages of the respective signals are set so that the gate signalof 0 V for generating potential wells and the gate signal ofapproximately -8 V for generating potential barriers are supplied fromthe CMOS shift register to the gate electrodes. In FIG. 9, the substratevoltage Vs is in the range of 15 to 25 V, the power source voltage Vccis about 0 V, and the voltage V_(L) is about -8 V.

Where the CMOS structure is used and the voltages are set up as justmentioned, the gate signal voltage at the gate electrode varies from -8to 12 V. Under this condition, high voltages ranging from 23 to 33 V aresometimes applied to the gate oxide films under the gate electrodesη_(p) of the p-channel MOS transistors of CMOS in the drive regions.This high voltage is in excess of a nominal breakdown voltage and candamage the oxide film.

The image pick-up device can also provide a frame storage mode, in whichan exposure state is set up and continued, and a field scan read for theodd-numbered field and a field scan read for the even-numbered field arealternately repeated at predetermined periods to produce an interlacescan read. In the field storage mode, the pixel signals of theodd-numbered and even-numbered fields are mixed and subjected to aone-time field scan read. This sequence is repeated twice to produce animage corresponding to one frame. At this time, if a moving object isphotographed in a still picture photographing mode, the time of readingone field is different from the time of reading the succeeding field, sothat the images of the fields read out are different from each other.Therefore, the picture quality of the reproduced image is deterioratedbecause the reproduced image is the combination of off-center images. Inthe field storage mode, the pixel signals of one line are formed usingtwo lines of pixel signals. Accordingly, the vertical resolution isreduced to a value corresponding to approximately one-half of the numberof pixels.

Referring to FIG. 3, the conventional CCD image pick-up device of theaccordion transfer type is based on the so-called frame transfer (FT)system in which the vertical charge transfer paths in the photodetectingarea provide both the charge transfer function and the optoelectrictransducing function. For this reason, the reproduced image suffers fromsmear. In the CCD image pick-up device, the vertical charge transferpaths are formed in the p-type substrate. Because of this, the overflowdrain function and the so-called substrate-free electronic shuttercannot be brought into full play. This makes it difficult to apply theimage pick-up device to a built-in camera in a video tape recorder,electronic still camera, and other types of image pick-up devices.

In the image pick-up device employing the p-well structure having theabove functions, a shift register circuit arrangement shown in FIG. 10is used to form gate signals in order to realize the charge transfer bythe accordion transfer system. However, the circuit arrangement involvesthe following problems.

As shown in FIG. 10, each bit of the shift register consists of a cellstructure enclosed by the dotted line. The required number of the cellsare connected in a cascade fashion to make up the shift register. Thecell structure of the first stage will typically be described. ThreeNMOS transistors u₁₁, u₁₂, and u₁₃ are inserted between a signal linefor a second clock signal φ₂ and an earth contact such that thesource-drain paths of those transistors are connected in series. Acapacitance C₁₁ made by using a gate oxide film is connected between thegate contact and the source contact of the transistor U₁₁. The gatecontact and the drain contact of the transistor u₁₂ are short circuited.The source-drain path of an additional transistor u₁₄ is insertedbetween the source contact of the transistor U₁₁ and ground while thegate contact is connected to a signal line for clock signal φ₁. NMOStransistors u₁₅ to u₁₈, and a capacitor C₁₂ make up a similar circuit.The drain contact of the transistor u₁₃ of the first circuit of the cellstructure is connected to the gate contact of the transistor u₁₅ of thesecond circuit.

The gate contact of the transistor U₁₁ constitutes an input contact ofthe cell structure. The drain contact of the transistor u₁₇ comprises anoutput contact and the gate contacts of the transistors u₁₃ and u₁₇comprise reset contacts. A plurality of these cells are connected suchthat the input contacts and the output contacts of the cells areconnected so as to form a cascade connection. A start pulse IM (or ST)is applied to the gate contact of the transistor u₁₁ of the first stagecell by way of an NMOS transistor u₀₀, which turns on and off insynchronism with the first clock signal φ₁.

In the cascade connection of the cells, the adjacent cells, for example,cells SE1 and SE2, are interconnected as shown. The gate contact of thetransistor u₁₃ in the first circuit of the cell SE1 is connected to thesource contact of the transistor u₁₁ in the first circuit of thesucceeding cell SE2. The gate contact of the transistor u₁₇ in thesecond circuit of the cell SE1 is connected to the source contact of thetransistor u₁₅ in the second circuit of the succeeding cell SE2. Thecell of the last stage is followed by a terminal circuit, as shown.

Bit output signals A₁, B₁, C₁, . . . , H₁ or A_(s), B_(s), C_(s), . . ., H_(s) generated at the source contacts of the transistors u₁₅ of therespective cells are applied to the transfer gates of the photodetectingarea A and the storage portion B, as shown in FIG. 3. The timing of thebit output signals, clock signals φ₁ and φ₂ and the start signal are asshown in FIG. 11.

In the conventional shift register thus constructed, as seen whenwatching times t₀, t₁, and t₂, the bit output signals A₁, B₁, C₁, . . ., H₁ or A_(s), B_(s), C_(s), . . . , H_(s) are output during every otherperiod of clock signal φ₁ or φ₂. Therefore, the transfer speed providedby the shift register is only 1/2 the transfer speed as defined by thefrequency of the clock signal φ₁ or φ₂. In other words, the frequency ofthe clock signal φ₁ or φ₂ must be twice the transfer frequency when thecharge is transferred in the vertical direction. This fact indicatesthat to realize the solid-state image pick-up device of high pixeldensity, a high frequency oscillator is required, making it difficult todesign the shift register.

Further, the conventional shift register cannot be reset until the startpulse reaches the cell of the last stage. Therefore, the propensity ofthe shift register rejects the resetting of the shift register atdesired times by an external controller. In this respect, the controlperformance of the shift register is not optimal.

SUMMARY OF THE INVENTION

The principal object of the present invention is to provide asolid-state image pick-up device of the charge-coupled device (CCD) typewhich can provide a clear reproduced image by using a so-callednoninterlace/full-frame read system which reads out all of the pixelsignals through one-time frame read operation using a system differentfrom the interlace/two-field scan read system employed in the prior art.

Another object of the present invention is to provide a solid-state CCDimage pick-up device which, when the image pick-up device incorporatesan electronic shutter in place of a mechanical shutter, can provide aclear reproduced image by using a so-called noninterlace/full-frame readsystem which reads out all of the pixel signals through one-time frameread operation.

A further object of the present invention is to provide a solid-stateCCD image pick-up device which is free from unwanted blooming in which avertical overflow drain structure is employed to drain excessive chargesof the photodiodes into the substrate. The overflow drain structureadvantageously can incorporate an electronic shutter function, which isoperable independent of the substrate, because of the charge drainage tothe substrate, and is operable in the full frame scan read mode suitablefor photographing a still picture because the image pick-up device is ofthe interline type and yet is capable of the full frame scan read.

Still another object of the present invention is to provide asolid-state CCD image pick-up device providing a function suitable forphotographing a motion picture in an interlace scan read mode and afunction suitable for photographing a still picture in anoninterlace/frame scan read mode.

Another object of the present invention is to provide a solid-state CCDimage pick-up device having an electronic shutter function and which isprovided with a shift register capable of generating gate signals for ascan read having increased vertical resolution.

These and other objects, features and advantages of the presentinvention are achieved by a solid-state image pick-up device of thecharge-coupled device type, comprising a plurality of optoelectrictransducing elements corresponding to pixels, the elements beingvertically and horizontally arrayed in a matrix fashion so as to formcolumn linear arrays and row linear arrays, the column linear arraysdefining a column direction and a plurality of vertical charge transferpaths, at least one of the vertical charge transfer paths beingassociated with a corresponding adjacent column linear array. Pixelsignals are vertically transferred from each of the column linear arraysto a corresponding one of the vertical charge transfer paths in a mannersuch that, after pixel signals generated in the pixels are transferredto the vertical charge transfer paths, gate signals occurring atpredetermined times are applied to gate electrodes of the verticalcharge transfer paths so as to permit the pixel signals to be scan readfrom the column linear arrays by the horizontal charge transfer paths.The image pick-up device further comprises switching elements providedfor each of a plurality of transfer gate electrodes coupled between adrive signal electrode and a pair of vertical transfer gate electrodesdisposed adjacent to each of the optoelectric transducing elements sothat the gate electrodes are combined in an order starting from the gateelectrode disposed closest to the horizontal charge transfer path intogroups each consisting of a predetermined number of gate electrodes. Adrive circuit sequentially generates a plurality of drive signals forthe groups of the gate electrodes during every period during which theswitching elements are rendered conductive and the pixel signals aretransferred to the horizontal charge transfer paths from the columnlinear arrays so as to allow a full frame scan read to be performedthrough the vertical charge transfer paths by supplying a predeterminednumber of timing signals, the predetermined number corresponding to thenumber of gate electrodes, to the gate electrodes as the drive signalsfrom the drive circuit.

According to another embodiment of the present invention, a solid-stateCCD image pick-up device comprises a vertical overflow drain structurefor draining excessive charges in a photodetecting area into asemiconductor substrate, a plurality of charge transfer paths formed infirst well layers buried in the semiconductor substrate and a pluralityof drive circuits formed in second well layers, the second well layersbeing formed at least one of separately from and integrally with thefirst well layers in the semiconductor substrate, wherein each of thedrive circuits comprises a plurality of transistors having a single MOSstructure.

According to another embodiment of the present invention, a solid-stateCCD image pick-up device comprises a plurality of optoelectrictransducing elements corresponding to pixels, the elements beingvertically and horizontally arrayed in a matrix fashion, a plurality ofvertical charge transfer paths each disposed between the adjacent lineararrays of optoelectric transducing elements which extend in the columndirection and a pair of gate electrodes for each of the vertical chargetransfer paths adjacent to the optoelectric transducing elements. Pixelsignals are vertically transferred from each of the column linear arraysto a corresponding one of the vertical charge transfer paths such that,after pixel signals generated in the pixels are transferred to thevertical charge transfer paths, gate signals occurring at predeterminedtimes are applied to the gate electrodes of the vertical charge transferpaths so as to permit the pixel signals to be scan read from the columnlinear arrays by a horizontal charge transfer path. The image pick-updevice photographs a motion picture by an interlace/2 field scan readsuch that, by application of the gate signals to the gate electrodes atthe predetermined times, the field scan read is performed twice whilethe pixel signals from two lines of pixel signals are mixed in thehorizontal charge transfer path.

Further, another embodiment of the present invention provides asolid-state CCD image pick-up device comprising a plurality ofoptoelectric transducing elements corresponding to pixels, the elementsbeing vertically and horizontally arrayed in a matrix fashion, thevertically arrayed elements defining a column direction, a plurality ofvertical charge transfer paths, each of the paths being operativelycoupled to a corresponding one of the linear arrays of optoelectrictransducing elements extending in the column direction, a pair of gateelectrodes coupled to each of the vertical charge transfer pathsadjacent to the optoelectric transducing elements and circuitry forsupplying a field shift signal for transferring pixel signals generatedin the optoelectric transducing elements to the vertical charge transferpaths at different times for odd-numbered fields and even-numberedfields. Pixel signals are vertically transferred from the column lineararrays to the vertical charge transfer paths such that, after pixelsignals generated in the pixels are transferred to the vertical chargetransfer paths, application of gate signals occurring at predeterminedtimes to the gate electrodes of the vertical charge transfer pathsprovides a scan read of the pixel signals from each of the column lineararrays by the horizontal charge transfer path. The image pick-up devicephotographs a motion picture in an interlace/2 field scan read mode suchthat a field scan read is performed two times by application of the gatesignals to the gate electrodes to allow transfer of pixel charges to thevertical charge transfer paths in an order starting from one of thepixel signals corresponding to the one of the pixels closest to thehorizontal charge transfer path.

Additionally, the present invention provides a solid-state CCD imagepick-up device comprising a plurality of optoelectric transducingelements corresponding to pixels, the elements being vertically andhorizontally .arrayed in a matrix fashion to provide column lineararrays and row linear arrays of the elements, the column linear arraysdefining a column direction, a plurality of vertical charge transferpaths, each of the paths being operatively coupled to a correspondingone of the optoelectric transducing elements and a pair of gateelectrodes for each of the vertical charge transfer paths adjacent tothe optoelectric transducing elements. A plurality of pixel signals arevertically transferred from each of the column linear arrays to acorresponding one of the vertical charge transfer paths such that, afterthe pixel signals are transferred to the vertical charge transfer paths,application of gate signals occurring at predetermined times to the gateelectrodes of the vertical charge transfer paths permit a scan read ofthe pixel signals for each of the column linear arrays by a horizontalcharge transfer path. The image pick-up device provides at least onephotograph of motion picture in an interlace/2 field scan read mode suchthat the field scan read is performed responsive to two applications ofthe gate signals to the gate electrodes to allow transfer of pixelcharges to the vertical charge transfer paths in an order starting fromone of the pixel signals provided by the pixel closest to the horizontalcharge transfer path.

To achieve the above objects, the present invention is directed to asolid-state CCD image pick-up device in which a plurality ofoptoelectric transducing elements corresponding to pixels are verticallyand horizontally arrayed in a matrix fashion, and in which verticalcharge transfer paths are each disposed between adjacent column lineararrays of optoelectric transducing elements defining a column direction,wherein pixel signals are vertically transferred from each of the columnlinear arrays to a corresponding one of the vertical charge transferpaths to permit, after pixel signals generated in the optoelectrictransducing elements are transferred to the vertical charge transferpaths, application of gate signals generated at predetermined times froma shift register to gate electrodes of the vertical charge transferpaths at predetermined times, wherein the pixel signals are scan readfrom the column linear arrays by a horizontal charge transfer path.

More specifically, the shift register comprises first, second and thirdtransistors having source-drain paths connected in series between afirst line providing a first timing signal and a predetermined voltageline, a bootstrap capacitor connected between the gate and source of thefirst transistor and a fourth transistor having a gate contact connectedto receive a second timing signal and having a drain contact connectedto both a gate contact and the drain contact of the second transistorand having a source contact connected to the predetermined voltage line.The shift register further comprises fifth, sixth and seventhtransistors having source-drain paths connected in series between a lineproviding a second timing signal and the predetermined voltage line, abootstrap capacitor connected between the gate and source of the fifthtransistor and an eight transistor having a gate contact connected toreceive the first timing signal, having a drain contact connected toboth the gate and drain contacts of the sixth transistor and having asource contact connected to the predetermined voltage line. The shiftregister further comprises a plurality of bit circuits each having acell structure in which a node between the second and third transistorsis connected to the gate contact of the fifth transistor, the gatecontact of the first transistor forms an input contact, and a nodebetween sixth and seventh transistors forms an output contact, whereinthe plurality of bit circuits are connected in a cascade fashion topermit the output contact of one bit circuit to be coupled to the inputcontact of the succeeding bit circuit.

According to one aspect of the present invention, a start pulse isapplied to the input contact of the least significant bit circuitthrough a switching element to be turned on and off in synchronism withthe second timing signal and a reset signal is applied to the gatecontacts of the third and seventh transistors and bit signals appearingat the output contacts of the bit circuits are applied to transfer gateelectrodes.

These and other objects, features and advantages of the invention aredisclosed in or apparent from the following description of preferredembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments are described with reference to the drawings,in which like elements are generally denoted by like or similar numbers,and in which:

FIG. 1 is a plan view showing the structure of a key portion of aconventional solid-state image pick-up device of the CCD type;

FIG. 2 is a diagram showing the charge transfer operation by theconventional device in terms of potential profiles.

FIG. 3 is a plan view showing the structure of a key portion of aconventional solid-state image pick-up device of the CCD type;

FIGS. 4(a) through 4(c) are diagrams showing the timing pattern of thedevice of FIG. 3;

FIGS. 5 and 6 are diagrams showing the transfer operations by theconventional device;

FIGS. 7 to 9 are circuit and schematic diagrams useful in explaining theproblems of the conventional device;

FIG. 10 is a circuit diagram showing a conventional shift register;

FIG. 11 is a timing chart showing the operation of the shift register ofFIG. 10;

FIG. 12 is a block and schematic diagram showing an electronic stillcamera incorporating a solid-state image pick-up device of the CCD typeaccording to an embodiment of the present invention;

FIG. 13 is a block and schematic diagram showing the solid-state imagepick-up device of the invention;

FIG. 14 is a diagram showing the construction of a key portion of aphotodetecting area of the image pick-up device, and its peripherycircuit arrangement;

FIGS. 15 and 16 are sectional views showing key portions of thestructure shown in FIG. 14;

FIG. 17 is a waveform roughly showing a scan read operation of the imagepick-up device;

FIGS. 18 through 23 are timing charts showing in detail the scan readoperation of the image pick-up device of the embodiment;

FIG. 24 is a circuit diagram showing a drive circuit used in anotherembodiment of the present invention;

FIGS. 25 through 32 are timing charts showing in detail the scan readoperation of the image pick-up device of the embodiment of FIG. 24;

FIG. 33 is a diagram showing the construction of a photodetecting areaof the image pick-up device, and its periphery circuit arrangementaccording to another embodiment of the invention;

FIGS. 34 to 37 are timing charts showing in detail the scan readoperation of the image pick-up device of the embodiment shown in FIG.33;

FIG. 38 is a circuit diagram showing a circuit arrangement of a shiftregister incorporated into another embodiment of the image pick-updevice; and

FIGS. 39 and 40 are timing charts useful in explaining the operation ofthe shift register shown in FIG. 38.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of a solid-state image pick-up device of thecharge-coupled device type according to the present invention will bedescribed with reference to the accompanying drawings. In thisembodiment, the image pick-up device is particularly suited forelectronic still cameras.

As shown in FIG. 12, the overall construction of the electronic stillcamera includes a pick-up optical system 1, a stop mechanism 2, and asolid-state image pick-up device 3 of the CCD type incorporating thepresent invention. These components are disposed side by side inalignment with one another with respect to an optical axis of thepick-up optical system 1. With the combination of those components, animage of an object is incident on the photodetecting area of thesolid-state image pick-up device 3. Preferably, the electronic stillcamera includes a signal processor 4 and a recording mechanism 5. Thesignal processor 4 applies color separation, γ-correction, white balanceadjustment, and the like to the pixel signals generated by thesolid-state image pick-up device 3. The recording mechanism 5advantageously applies modulation processing to the luminance signal andthe color difference signal generated from the recording mechanism 5,thereby converting them into a signal format advantageously suited torecording operations. A sync control circuit 6 synchronously controlsthe operation of the stop mechanism 2, read times of the solid-stateimage pick-up device 3, and the operation of the signal processor 4 andthe recording mechanism. 5. The still camera, under the control of thesync control circuit 6, provides a sequence of operations including theimage pick-up and recording.

The construction of the solid-state image pick-up device 3 is as shownin FIG. 13, and it includes a photodetecting area 7 including aplurality of matrix-arrayed photodiodes, generally denoted P,corresponding to pixels and vertical charge transfer paths L_(l) toL_(m) each disposed between the adjacent linear arrays of photodiodes,which extend in the column direction Y. A horizontal charge transferpath 8 is formed and located at one end of the vertical charge transferpaths L_(l) to L_(m). An output amplifier 9 is formed and located at oneend of the horizontal charge transfer path 8.

In connection with the vertical charge transfer paths L_(l) to L_(m),gate electrodes are provided as discussed in greater detail below. Alight shield layer advantageously is provided over the structure toshield light incident on the upper surface. First, second and thirddrive circuits 10, 11 and 12, respectively, supply signals to the gateelectrodes to cause the vertical charge transfer paths L_(l) to L_(m) totransfer charges at predetermined times. The sync control circuit 6 ofFIG. 12 generates a start pulse and timing signals φ_(L), φ_(G), φ_(FS),φ_(S), φ₁, φ₂, φ₃, and φ₄, which are supplied to the drive circuits 10,11, and 12.

The horizontal charge transfer path 8, which receives signal chargestransferred from the vertical charge transfer paths L_(l) to L_(m), isprovided with gate electrodes for horizontally transferring the receivedsignal charges to an output amplifier 9. Gate signals supplied from thesync control circuit 6, are applied to the gate electrodes, causing thehorizontal transfer of signal charges.

The structure of the photodetecting area 7 and the circuit arrangementsof the drive circuits 10, 11, and 12 coupled with the area will bedescribed with reference to FIGS. 14, 15 and 16. FIG. 14 is a plan viewshowing a key portion of the photodetecting area 7, as viewed from thephotodetecting surface. FIG. 15 is a sectional view taken along linex--x in FIG. 14, while FIG. 16 is a sectional view taken along line y--yin FIG. 14.

In these figures, p-well layers 14, 15 and 16 are formed in the surfaceregion of an n-type semiconductor substrate 13. The p-well layer 14 isprovided for forming the photodetecting area 7. The p-well layer 14 isalso used in forming the first drive circuit 10. The p-well layer 16 isused in forming the second and third drive circuits 11 and 12. Therelated circuits advantageously are formed in p-well layers 14, 15, and16.

In the photodetecting area 7, a plurality of impurity layers 17 made ofn⁺ impurity are formed in the column direction Y and the row direction Xinto a matrix array of photodiodes denoted as P in FIG. 13. A pluralityof n-type impurity layers 18 (indicated by dotted lines in FIG. 16) areformed between the adjacent linear arrays of impurity layers 17, whichextend in the column direction Y to form the vertical charge transferpaths L_(l) to L_(m) shown in FIG. 13. A plurality of p⁺ impurity layers19 are formed, in a surrounding fashion, in the portions exclusive ofthe portions to serve as transfer gates denoted as Tg (only one portionis typically illustrated in FIG. 14), the photodiode portions, and theportions of the vertical charge transfer paths to form channel stopperregions (shaded portions enclosed by dotted lines in FIG. 14).

In FIG. 14, the horizontal linear arrays of photodiodes P (FIG. 13) aredenoted, in order from the bottom, as P₁, P₂, P₃, . . . , P₆,respectively. Gate electrodes G₁₁ to G₄₁, G₁₂ to G₁₃ to G₄₃, . . .G_(1n) to G_(4n), each consisting of paired polycrystalline siliconlayers, are layered on the upper surfaces of the vertical chargetransfer paths L_(l) to L_(n), while being respectively adjacent to thehorizontal linear arrays of photodiodes P₁, P₂, P₃, . . . , P₆. As shownin FIGS. 14 and 15, the odd-numbered gate electrodes, G₁₁, G₃₁, G₁₂,G₃₂, G₁₃ and G₃₃, for example, are designed to have a narrow width W1,while the even-numbered gate electrodes, such as G₂₁, G₄₁, G₂₂, G₄₂, G₂₃and G₄₃, are designed to have a wide width W2. Here, those gateelectrodes are counted, with the gate electrode G₁₁, as the first gateelectrode.

Gate signals φ₁₁, φ₂₁, φ₃₁, φ₄₁, φ₁₂, φ₂₂, φ₃₂, and φ₄₂ are applied atpredetermined times (discussed below) to the gate electrodes so thatpotential wells (referred to as transfer pixels) and potential barriers,which are for charge transfer, are generated in the vertical chargetransfer paths under the gate electrodes. When a predetermined highvoltage is applied to the even-numbered gate electrodes G₂₁, G₄₁, G₂₂,G₄₂, G₂₃ and G₄₃, the transfer gates Tg become conductive. The transferpixels, which are generated under the even-numbered gate electrodes G₂₁,G₄₁, G₂₂, G₄₂, G₂₃ and G₄₃ located adjacent to the horizontal lineararrays of photodiodes P₁, P₂, P₃, . . . , P₆ become conductive. Underthis condition, transfer of signal charges from the photodiodes to thetransfer pixels is allowed.

As shown in FIG. 14, the horizontal charge transfer path 8 is formed inthe location at the end of the vertical charge transfer paths L_(l) toL_(m), and gate electrodes are provided for horizontally transferringsignal charges at the times providing either a four- or a two-phasedrive system.

A circuit arrangement of the first drive circuit 10 will be describedwith reference to FIGS. 14 and 16. The leading end of the odd-numberedgate electrodes G₁₁, G₃₁, G₁₂, G₃₂, G₁₃ and G₃₃ are connected to asignal line providing a V_(L), through NMOS transistors M₁₁, M₃₁, M₁₂,M₃₂, M₁₃ and M₃₃. The leading ends of the even-numbered gate electrodesG₂₁, G₄₁, G₂₂, G₄₂, G₂₃ and G₄₃ are connected to a signal line providinga drive signal φ_(H), through NMOS transistors M₂₁, M₄₁, M₂₂, M₄₂, M₂₃and M₄₃. It will be apparent that the gate electrode G₁₁ closest to thehorizontal charge transfer path 8 is counted as the first gateelectrode. A drive signal φ_(G) is applied to the gate contacts of thosetransistors.

The leading ends of the even-numbered gate electrodes G₂₁, G₄₁, G₂₂,G₄₂, G₂₃ and G₄₃ are connected to the emitter contacts of npntransistors Q₂₁, Q₄₁, Q₂₂, Q₄₂, Q₂₃ and Q₄₃, respectively. A drivesignal φ_(FS) is applied to the base contacts of those transistors, andvoltage V_(S) is applied to the collector contacts.

Each NMOS transistor is constructed from a pair of n⁺ impurity layers 20and 21, and a gate electrode layered on the surface portion, as shown inthe structure within the p-well layer 15 in FIG. 16. A drive signalφ_(H) is coupled with the n⁺ impurity layer 20 to serve as a draincontact. The n⁺ impurity layer 21 to serve as a source contact isconnected to the gate electrode on the vertical charge transfer path.The signal V_(L) is applied to a p⁺ impurity layer 22 buried in thep-well layer 15. The npn transistor includes a p⁺ impurity layer 23buried in the p-well layer 15, an n⁺ impurity layer 24 and an n-typesemiconductor substrate 13. The n⁺ impurity layer 24 serving as anemitter contact is connected to the gate electrodes. A timing signalφ_(FS) is applied to the p-well layer 15, serving as the base contactand the p⁺ impurity layer 23. A bias voltage Vs for the substrate 13 isapplied to the n-type semiconductor substrate 13 serving as thecollector contact. The second drive circuit 11 includes NMOS transistorsm₁₁ to m_(4n) which select the timing signals φ₁ to φ₄ from the synccontrol circuit 6 in synchronism with drive signals S_(l) to S_(n)generated from the third drive circuit 12. The NMOS transistors aregrouped into quartets of transistors. The drive signals S₁, S₂, S₃ andS₄ are sequentially applied to their gate contacts. The timing signal φ₁is applied to the drain contacts of the first NMOS transistors m₁₁, m₁₂,m₁₃ and m₁₄, timing signal φ₂ is applied to the drain contacts of thesecond NMOS transistors m₂₁, m₂₂, m₂₃ and m₂₄, timing signal φ₃ isapplied to the drain contacts of the third NMOS transistors m₃₁, m₃₂,m₃₃ and m₃₄ and timing signal φ₄ is applied to the drain contacts of thefourth NMOS transistors m₄₁, m₄₂, m₄₃ and m₄₄. The signals φ₁₁, φ₂₁, φ₃₁and φ₄₁ coupled with the source contacts of the NMOS transistors m₁₁,m₂₁, m₃₁ and m₄₁ in FIG. 14, respectively, correspond to the timingsignals φ₁, φ₂, φ₃, and φ₄.

As shown, gate electrodes are connected, starting with gate electrodeG₁₁ closest to the horizontal charge transfer path 8, to the sourcecontacts of the NMOS transistors.

The third drive circuit 12 includes a shift register for producing drivesignals S_(l) to S_(n) at predetermined times, as discussed in greaterdetail below.

Second and third drive circuits 11 and 12 are each composed of an NMOStransistor formed in the p-well layer 16 shown in FIG. 16, and otherelectronic components. A plurality of n⁺ impurity layers 25 and 26forming an NMOS transistor and a gate contact, by way of example, areformed in the p-well layer 16, as shown in FIG. 16.

The operation of the image pick-up device when it takes a still picturewill be described with reference to FIG. 17. It is assumed that theperiod T_(VB) corresponds to the vertical blanking period of a standardtelevision system, i.e., an NTSC television system. At a predeterminedtime during the period T_(VB), a so-called field shift is performed toshift the pixel charges from the photodiodes to the vertical chargetransfer paths. For the electronic shutter function, the time of thefield shift operation corresponds to a time at which a shutter isclosed, i.e., exposure completion. Accordingly, the exposure operationstarts at a time after the shutter close time, and the device operatesso that the exposure time ranges from the exposure start time to a timeof starting the field shift operation. The unnecessary charges possiblycausing the smear component and the dark current component in thevertical charge transfer paths L_(l) to L_(m) and the horizontal chargetransfer path 8, are discharged by the charge transfer operation beforethe field shift starts. Further, immediately before the exposure starts,the unnecessary charges in the photodiodes are drained by the verticaloverflow drain structure.

During the period T_(VB) corresponding to the vertical blanking periodof the standard television system, the pixel signals of all of thephotodiodes are simultaneously transferred to the transfer pixels of thevertical charge transfer paths L_(l) to L_(m). During the period T_(HB)corresponding to the horizontal blanking period, a pixel signal of thetransfer pixel closest to the horizontal charge transfer path 8 istransferred to the transfer path 8. During a period T_(1H) correspondingto the horizontal scan period (called a 1 H period), the pixel signalsof one line are horizontally transferred through the horizontal chargetransfer path 8. As a result, the pixel signals of the first line areread out.

Then, during the period T_(HB) corresponding to the next horizontalblanking period, the vertical charge transfer paths L_(l) to L_(m) feedthe pixel signals of the next line to the horizontal charge transferpath 8. During a period T_(1H) corresponding to the next horizontal scanperiod, the pixel signals are horizontally transferred through thehorizontal charge transfer path 8. In this way, the pixel signals of thesecond line are read out.

The pixel signals of the third line are likewise read out of thephotodiodes during periods T_(HB) and T_(1H). The pixel signals of theremaining lines are successively read out while repeating this sequenceof operations. Finally, all of the pixel signals of one frame are readout.

The scan read operation will be described in greater detail withreference to FIG. 18, which shows a timing chart for drive signals andtiming signals. In FIG. 18, the period T_(VB) corresponds to thevertical blanking period, period T_(HB) corresponds to the horizontalblanking period and period T_(1H) corresponds to the horizontal scanperiod. Further, "H" indicates a voltage of about 12 V, "M" indicates avoltage of about 0 V, "L" indicates a voltage of about -8 V and "HH"indicates approximately 15 to 25 V, which is equal to the substratevoltage.

During the period T_(VB) corresponding to the vertical blanking period,the timing signal φ_(H) goes high (H) only at a predetermined time t2,and remains at a level "M" during the remaining time. The timing signalφ_(G) is always at the "M" level. The timing signal φ_(FS) goes high asthe timing signal φ_(H) goes high, and is kept at the "L" level duringthe remaining time. The drive signals S_(l) to S_(n) generated from thethird drive circuit 12 are always at the "L" level.

During the period T_(VB), all of the NMOS transistors of the first drivecircuit 10 are rendered conductive by the timing signal φ_(G) at the "M"level, while at the same time all of the drive signals S_(l) to S_(n) ofthe third drive circuit 12 are set at the "L" level. Accordingly, all ofthe NMOS transistors in the second drive circuit 11 become conductive.All of the gate electrodes G₁₁, G₂₁, G₃₁, G₄₁ to G_(1n), G_(2n), G_(4n)are controlled by the first drive circuit 10.

More specifically, when the timing signals φ_(H) and φ_(FS) are not atthe "H" level, the gate signals φ₁₁, φ₃₁, φ₁₂, φ₃₂ to φ_(1n), φ_(3n),which are applied to the odd-numbered gate electrodes G₁₁, G₃₁, G₁₂, G₃₂to G_(1n), G_(3n), are each equal in voltage level to the signal V_(L)(constantly set at -8 V). Under this condition, potential barriers aregenerated in the vertical charge transfer paths L_(l) to L_(m) underthose gate electrodes.

The gate signals φ₂₁, φ₄₁, φ₂₂, φ₄₂ to φ_(2n), φ_(4n), which are appliedto the even-numbered gate electrodes G₂₁, G₄₁, G₂₂, G₄₂ to G_(2n),G_(4n), are each equal in voltage to the signal φ_(H) at the "M" level.Under this condition, transfer pixels are generated in the verticalcharge transfer paths L_(l) to L_(m) under those gate electrodes.

Accordingly, all of the portions adjacent to the transfer gates Tg (seeFIG. 14) serve as the transfer pixels being separated from one anotherby the potential barriers.

Under this condition, when the timing signals φ_(H) and φ_(FS) go highat time t2, all of the npn transistors Q₂₁, Q₄₁, Q₆₁, etc., becomeconductive and the "H" level voltage of approximately 12 V is applied toonly the even-numbered gate electrodes G₂₁, G₄₁, G₂₂, G₄₂ to G_(2n),G_(4n). Accordingly, all of the transfer gates Tg become conductive, andall of the pixel signals of the photodiodes are transferred to theadjacent transfer pixels.

As already described referring to FIG. 17, the exposure process has beencompleted just before the time t₂, and the removal of the unnecessarycharges has also been completed. During the period T_(VB), a so-calledfield shift operation is performed, so that at the time t2 in FIG. 22,the pixel signals (marked as shaded squares) are transferred to thevertical charge transfer paths. FIG. 22 is a view showing the chargetransfer operation of one vertical charge transfer path. During theperiod T_(HB) corresponding to the first horizontal blanking period, thetiming signal φ_(G) is always at the "L" level. Accordingly, all of theNMOS transistors in the first drive circuit 10 become nonconductive andare separated from all of the gate electrodes.

Only the drive signal S1 at the first output terminal of the third drivecircuit 12 is set at the "M" level, while the remaining drive signals S₂to S_(n), are at the "L" level. This renders only the first set of NMOStransistors m₁₁, m₂₁, m₃₁, m₄₁ conductive due to the drive signal S₁ ofthe second drive circuit 11.

During the period when only the drive signal S₁ is set at the "M" level,the timing signals φ₁, φ₂, φ₃, and φ₄ of four phases for the verticalcharge transfer are supplied to the second drive circuit 11.Accordingly, only the first set of gate signals φ₁₁, φ₂₁, φ₃₁, and φ₄₁are equal in level to the timing signals φ₁, φ₂, φ₃, and φ₄. The chargetransfer is performed by the first set of gate electrodes G₁₁, G₂₁, G₃₁,and G₄₁. The enlarged signal waveforms during the period T_(HB) areshown in FIG. 19.

As a consequence, the signal charges are transferred to the horizontalcharge transfer path 8 at the times (indicated by numerals 1, 2, 3, 4,5, 6, and 7) of the gate signals φ₁₁, φ₂₁, φ₃₁, and φ₄₁ in FIG. 19, asin the first transfer shown in FIG. 22. A pixel signal q_(1j) of thefirst line closest to the horizontal charge transfer path 8 istransferred to the transfer path 8. A pixel signal q_(2j) of the secondline moves to the first line position.

Then, during the first horizontal scan period T_(1H) (between times t₄and t₅), the variation of the signal applied to each gate electrodestops, and the horizontal charge transfer path 8 vertically transferssignal charges in synchronism with the gate signals α₁ to α₄ recurringat predetermined times according to the four- or two-phase drive system.As a result, pixel signals of the first line are read out.

During a period between times t₅ to t₇, a sequence of operations, whichis similar to that during the period between times t₃ to t₅, is repeatedto read the pixel signals of the next line out of the image pick-updevice. During the horizontal blanking period T_(HB) between times t₃ tot₄, the drive signals S₁ and S₂ of the third drive circuit 12 aresimultaneously set to the "M" level and the remaining drive signals S₃to S_(n) are set to the "L" level. The enlarged signal waveforms duringthis period T_(HB) are shown in FIG. 20.

Consequently, a set of the first to fourth gate electrodes G₁₁ to G₄₁,and two sets of fifth to eighth gate electrodes G₁₂ to G₄₂ are driven bythe gate signals φ₁₁ to φ₄₁ and φ₁₂ to φ₄₂, which are equal to thetiming signals φ₁, φ₂, φ₃, and φ₄. The result is the vertical transferof the pixel signals under those gate electrodes.

The timing chart shown in FIG. 20 shows that as indicated by the secondvertical scan in FIG. 22, the pixel signal q_(2j) of the second line istransferred to the horizontal charge transfer path 8. Two lines of thepixel signals q_(3j) of the third line and one line of the pixel signalq_(4j) of the fourth line are transferred to the horizontal chargetransfer path 8.

During the horizontal scan period T_(1H) between times t₆ and t₇, thehorizontal charge transfer path 8 reads out the pixel signal q_(2j) ofthe second line.

The third scan read starts at time t₇. Then, the drive signals S₁, S₂,and S₃ are set at the "M" level, while the remaining drive signals S₄ toS_(n) of the third drive circuit 12 are set at the "L" level. The firstto third sets of first to 12th gate electrodes G₁₁ to G₄₁, G₁₂ to G₄₂ toG₄₂, and G₁₃ to G₄₂ are driven for the vertical charge transfer.Accordingly, as in the third transfer of FIG. 22, the pixel signalq_(3j) of the third line is transferred to the horizontal chargetransfer path 8. The pixel signals q_(4j) to q_(7j) of the 4th to 7thlines are transferred every line to the horizontal charge transfer path8.

Then, the pixel signal q_(3j) is read out of the photodiodes by thehorizontal charge transfer path 8.

Subsequently, the drive signals S₄ to S_(n) of the third drive circuit12 are progressively inverted to "M" level every time the pixel signalof each line is read out. The gate electrodes to be driven are increasedevery four gate electrodes. During the horizontal blanking period T_(HB)(between times t₉ and t₁₀), all of the gate signals φ₁₁ to φ_(4n) havethe same waveforms as those of the timing signals φ₁ to φ₄, as shown inFIG. 21. The pixel signals of the last line are read out by the finalscan read operation.

FIG. 23 shows the K-th and (K+1)th vertical charge transfer operations,for example, in terms of potential profiles. As shown, in order from thetransfer pixel closest to the horizontal charge transfer path 8, theintervals of the idle transfer pixels progressively increase. With thisthe pixel signals are progressively read out in the order from the pixelsignal closest to the transfer path 8 to the succeeding ones.

It will be appreciated that, in the present embodiment, the pixelsignals of one frame can be read out by a single frame scan readoperation.

The width of the odd-numbered gate electrodes is wider than that of theeven-numbered gate electrodes. This feature advantageously allows anincrease in a charge retaining capacitance of the transfer pixelsadjacent to the transfer gates. Additionally, during the vertical chargetransfer, the transfer pixels under the even-numbered gate electrodesare used for the charge transfer, thereby improving the charge transferefficiency.

It will also be apparent that the charge transfer is performed insynchronism with the four-phase timing signals φ₁, φ₂, φ₃, and φ₄ duringthe period T_(HB) corresponding to each horizontal blanking period. Ifnecessary, timing signals having four or more phases may be used fordriving the gate electrodes corresponding to the number of phases.

The solid-state image pick-up device thus arranged can read all of thepixel signals of one frame through one-time frame scan read operation.Therefore, exposure through the electronic shutter can be applied to allof the pixel signals under the same conditions. Accordingly, the imagepick-up device can reproduce a clear image having a high verticalresolution.

As described above, in the solid-state image pick-up device of the CCDtype according to the invention, the exposure is performed at thegrouped optoelectric transducing elements corresponding to the pixelsallowing the pixel signals generated in the optoelectric transducingelements to be read out through the vertical and horizontal chargetransfer paths by a full-frame scan read operation. Accordingly, stillpicture reproduction is clear.

It will be appreciated that the solid-state CCD image pick-up deviceprovides a so-called electronic shutter function such that apredetermined voltage applied to the semiconductor substrate to drainexcessive or unnecessary charges into the substrate, and the exposurestarts at the time of completing the excessive charge drainage.

Additionally, the paired gate electrodes adjacent to each other causethe transfer paths to generate therein the transfer pixels and potentialbarriers. Accordingly, the transfer paths can transfer charges whilepreventing the charges from being mixed. This realizes the mostefficient charge transfer and provides a means to effectively improvethe vertical resolution.

Another preferred embodiment of the present invention, which includes athird drive circuit 12, will be described with reference to FIG. 24. Thethird drive circuit 12 consists of a shift register for shifting a startpulse φ_(s) in synchronism with two-phase clock signal φ_(A) and φ_(B)to sequentially generate drive signals of logic "H" in the order fromthe low- order bit to the high-order bit. In the first period, only thefirst drive signal S1 goes high ("H"), while the remaining high-orderbits are all low ("L") in logic level. In the second period, twolow-order bits S₁ and S₂ go high, while the remaining high-order bitsare low. In the third period, three low-order bits S₁, S₂, and S₃ gohigh, while the remaining high-order bits are low. Thus, the number ofhigh drive signals progressively increases in order from the low-orderbits to the high-order bits.

As shown in FIG. 24, each bit has a corresponding cell structure, andhence the circuit of the first bit will be typically described. Thesource-drain paths of three MOS u₁₁, u₁₂, u₁₃, and u₁₄ are connected inseries between a signal line of the voltage V_(L) and a signal line ofthe clock signal φ_(B). A signal line for the reset signal RS isconnected to the gate contact of the transistor u₁₃. A bootstrapcapacitor ε₁₁ is connected between the gate contact and the draincontact of the transistor μ₁₁. The gate contact and the source contactof the transistor u₁₂ are connected to each other, and to the sourcecontact of the transistor u₁₄. The transistor u₁₄ is connected at thedrain contact to the signal line for the voltage V_(L) and at the gatecontact to the signal line for the clock signal φ_(A).

Transistors MOS U₂₂, U₂₂, U₂₃, and u₂₄ make up the same circuit as thatmade up of the transistors MOS u₁₁, u₁₂, u₁₃, and u₁₄. The drain contact(output point) of the transistor u₁₂ is connected to the gate contact(input point) of the transistor u₂₂. However, the connection of thesignals φ_(A) and φ_(B) thereto is inverted.

The bit input corresponds to the gate contact of the gate contact of thetransistor u₁₁. The bit output corresponds to the drain contact of thetransistor u₂₂. An n-bit shift register is formed by connecting theinputs and outputs of those bit cells in a cascade fashion. A startpulse φ_(s) is inputted to the least significant bit cell through ananalog switch u₀₀ which is rendered conductive in synchronism with theclock signal φ_(A).

The second and third drive circuits 11 and 12 are each composed of anNMOS transistor formed in the p-well layer 16 shown in FIG. 16, andother electronic components. A plurality of n⁺ impurity layers 25 and 26forming an NMOS transistor and a gate contact, by way of example, areformed in the p-well layer 15 shown in FIG. 6.

The scan read operation will be described in detail with reference toFIG. 18 showing a timing chart of drive signals and timing signals. Inthe figure, the period T_(VB) corresponds to the vertical blankingperiod, the period T_(HB) corresponds to the horizontal blanking period,and the period T_(1H) corresponds to the horizontal scan period.Further, "H" indicates a voltage of 12 V, "M" is a voltage of about 0 V,"L" is a voltage of about -8 V, and "HH" is approximately 15 to 25 V,which is equal to the substrate voltage. The operation of this preferredembodiment will be discussed while referring generally to FIGS. 17-23.

During the period T_(VB) corresponding to the vertical blanking period,the timing signal φ_(H) goes high (H) at a predetermined time t2, and isat the "M" level at the remaining time. The timing signal φ_(G) isalways at the "M" level. The timing signal φ_(FS) goes high (H) as thetiming signal φ_(H) goes high, and is kept at the "L" level at theremaining time. The drive signals S_(l) to S_(n) generated from thethird drive circuit 12 are always at the "L" level.

During the period T_(VB), all of the NMOS transistors of the first drivecircuit 10 are rendered conductive by the timing signal φ_(G) at the "M"level, while at the same time all of the drive signals S_(l) to S_(n) ofthe third drive circuit 12 are set to the "L" level. Accordingly, all ofthe NMOS transistors in the second drive circuit 11 become conductive.All of the gate electrodes G₁₁, G₂₁, G₃₁, G₄₁ to G_(1n), G_(2n), G_(4n)are controlled by the first drive circuit 10.

More specifically, when the timing signals φ_(H) and φ_(FS) are not atthe "H" level, the gate signals φ₁₁, φ₃₁, φ₁₂, φ₃₂ to φ_(1n), φ_(3n),which are applied to the odd-numbered gate electrodes G₁₁, G₃₁, G₁₂, G₃₂to G_(1n), G_(3n), are each equal in voltage level to the signal V_(L)(constantly set at -8 V). Under this condition, potential barriers aregenerated in the vertical charge transfer paths L_(l) to L_(m) underthose gate electrodes.

The gate signals φ₂₁, φ₄₁, φ₂₂, φ₄₂ to φ_(2n), φ_(4n), which are appliedto the even-numbered gate electrodes G₂₁, G₄₁, G₂₂, G₄₂ to G_(2n),G_(4n), are each equal in voltage to the signal φ_(H) at the "M" level.Under this condition, transfer pixels are generated in the verticalcharge transfer paths L_(l) to L_(m) under those gate electrodes.

Accordingly, all of the portions adjacent to the transfer gates Tg (seeFIG. 14) serve as the transfer pixels being separated from one anotherby the potential barriers.

Under this condition, when the timing signals φ_(H) and φ_(FS) go highat time t2, all of the npn transistors Q₂₁, Q₄₁, Q₆₁, . . . becomeconductive, and the "H" level voltage of approximately 15 to 25 V isapplied to only the even-numbered gate electrodes G₂₁, G₄₁, G₂₂, G₄₂ toG_(2n), G_(4n). Accordingly, all of the transfer gates Tg becomeconductive, and all of the pixel signals of the photodiodes aretransferred to the adjacent transfer pixels.

During the period T_(VB), a so-called field shift operation isperformed, so that as at the time t2 shown in FIG. 22, the pixel signals(marked as black squares) are transferred to the vertical chargetransfer paths.

During the period T_(HB) corresponding to the first horizontal blankingperiod, the timing signal φ_(G) is always at the "L" level. Accordingly,all of the NMOS transistors in the first drive circuit 10 becomenonconductive and are separated from all of the gate electrodes.

Only the drive signal S1 at the first output terminal of the third drivecircuit 12 is set at the "M" level, while the remaining drive signals S₂to S_(n), are at the "L" level. This renders conductive only the firstset of NMOS transistors m₁₁, m₂₁, m₃₁, m₄₁ concerning the drive signalS₁ of the second drive circuit 11.

During the period that only the drive signal S₁ is set to "M" level, thetiming signals φ₁, φ₂, φ₃, and φ₄ of four phases for the vertical chargetransfer are inputted to the second drive circuit 11. Accordingly, onlythe first set of first to fourth gate signals φ₁₁, φ₂₁, φ₃₁, and φ₄₁ areequal in level to the timing signals φ₁, φ₂, φ₃, and φ₄. The chargetransfer is performed by the first set of first to fourth gateelectrodes G₁₁, G₂₁, G₃₁, and G₄₁. The enlarged signal waveforms duringthe period T_(TB) are shown in FIG. 19.

Consequently, the signal charges are transferred to the horizontalcharge transfer path 8 at the times (indicated by numerals 1, 2, 3, 4,5, 6, and 7) of the gate signals φ₁₁, φ₂₁, φ₃₁, and φ₄₁ in FIG. 9, as inthe first transfer shown in FIG. 22. A pixel signal q_(1j) of the firstline closest to the horizontal charge transfer path 8 is transferred tothe transfer path 8. A pixel signal q_(2j) of the second line moves tothe first line position.

Then, during the first horizontal scan period T_(1H) (between times t₄and t₅), the variation of the signal applied to each gate electrodestops, and the horizontal charge transfer path 8 vertically transferssignal charges in synchronism with the gate signals α₁ to α₄ recurringat predetermined times according to the four- or two-phase drive system.As a result, pixel signals of the first one line are read out.

During a period between times t₅ to t₇, a sequence of operations, whichis similar to that during the period between times t₃ to t₅, is repeatedto read the pixel signals of the next line out of the image pick-updevice. During the horizontal blanking period T_(HB) between times t₃ tot₄, the drive signals S₁ and S₂ of the third drive circuit 12 aresimultaneously set to "M" level, and the remaining drive signals S₃ toS_(n) are set to "L" level. The enlarged signal waveforms during thisperiod T_(HB) are shown in FIG. 20.

As a result, a set of the first to fourth gate electrodes G₁₁ to G₄₁,and two sets of fifth to eighth G₁₂ to G₄₂ are driven by the gatesignals φ₁₁ to φ₄₁ and φ₁₂ to φ₄₂, which are equal to the timing signalsφ₁, φ₂, φ₃, and φ₄. The result is the vertical transfer of the pixelsignals under those gate electrodes.

The timing chart shown in FIG. 20 shows that as indicated by the secondvertical scan in FIG. 22, the pixel signal q_(2j) of the second line istransferred to the horizontal charge transfer path 8. Two lines of thepixel signals q_(1j) of the third line and one line of the pixel signalof the fourth line are transferred to the horizontal charge transferpath 8. During the horizontal scan period T_(1H) between times t₆ andt₇, the horizontal charge transfer path 8 reads out the pixel signalq_(2j) of the second line.

The third scan read starts at time t₇. Then, the drive signals S₁, S₂,and S₃ are set to "M" level, while the remaining drive signals S₄ toS_(n) of the third drive circuit 12 are set to "L" level. The first tothird sets of first to 12th gate electrodes G₁₁ to G₄₁, G₁₂ to G₄₂ toG₄₂, and G₁₃ to G₄₂ are driven for the vertical charge transfer.Accordingly, as in the third transfer of FIG. 12, the pixel signalq_(3j) of the third line is transferred to the horizontal chargetransfer path 8. The pixel signals q_(4j) to q_(5j) of the 4th to 6thlines are transferred every two lines to the horizontal charge transferpath 8. The pixel signal q_(6j) of one line is transferred to there.

Then, the pixel signal q_(3j) is read out of the photodiodes by thehorizontal charge transfer path 8.

Subsequently, the drive signals S₄ to S_(n) of the third drive circuit12 are progressively inverted to "M" level every time the pixel signalof each line is read out. The gate electrodes to be driven are increasedevery four gate electrodes. During the horizontal blanking period T_(HB)(between times t₉ and t₁₀), all of the gate signals φ₁₁ to φ_(4n) havethe same waveforms as those of the timing signals φ₁ to φ₄, as shown inFIG. 11. The pixel signals of the last line are read out by the finalscan read operation.

FIG. 23 shows the K-th and (K+1)th vertical charge transfer operations,for example, in terms of potential profiles. As shown, in order from thetransfer pixel closest to the horizontal charge transfer path 8, theintervals of the idle transfer pixels progressively increase. With this,the pixel signals are progressively read out in the order from the pixelsignal closest to the transfer path 8 to the succeeding ones.

The preferred embodiment of the present embodiment discussed immediatelyabove comprises a drive circuit for supplying the gate signal to thegate electrode constructed with MOS transistors of the NMOS structure,not CMOS structure, and transistors of the bipolar structure.Accordingly, the resultant drive circuits have a high breakdown voltage,and allow the vertical overflow drain and the electronic shutterfunction to be advantageously incorporated.

With provision of the vertical overflow drain structure, the excessivecharges of the photodiodes can be drained into the substrate, removingunwanted phenomenon including blooming. Preferably, an electronicshutter which does not use the substrate is formed, and with theelectronic shutter, the noninterlace/full frame read is possible. Inthis respect, the image pick-up device is suitable for photographing astill picture.

In the image pick-up device thus constructed, high breakdown performanceis realized because the impurity concentration of the semiconductorsubstrate and the well layer is relatively low. The breakdownperformance realized is enough to withstand the high voltage needed torealize the vertical overflow drain function, and also the high voltageneeded to operate the electronic shutter.

According to the present invention, a well layer is formed in thesemiconductor substrate, a circuit using MOS transistors of a singlestructure is formed in the well layer. Therefore, the resultant imagepick-up device is improved in breakdown voltage performance, and thevertical overflow drain structure and the electronic shutter functionmay be introduced into the device.

Another preferred embodiment of the present invention, including amodified form of the third drive circuit 12, will be described withreference to FIG. 24. The third drive circuit 12 includes a shiftregister for shifting a start pulse φ_(s) in synchronism with two-phaseclock signal φ_(A) and φ_(B) to sequentially generate drive signals oflogic "H" in the order from the low- order bit to the high-order bit. Inthe first period, only the first drive signal S₁ goes high ("H"), whilethe remaining high-order bits are all low ("L") in logic level. In thesecond period, two low-order bits S₁ and S₂ go high, while the remaininghigh-order bits are low. In the third period, three low-order bits S₁,S₂, and S₃ go high, while the remaining high-order bits are low. Thus,the number of high drive signals progressively increases in order fromthe low-order bits to the high-order bits.

As shown in FIG. 24, each bit has a cell structure, and hence thecircuit of the first bit will be typically described. The source-drainpaths of three MOS u₁₁, u₁₂, u₁₃, and u₁₄ are connected in seriesbetween a signal line of the voltage V_(L) and a signal line of theclock signal φ_(B). A signal line for the reset signal RS is connectedto the gate contact of the transistor u₁₃. A bootstrap capacitor ε₁₁ isconnected between the gate contact and the drain contact of thetransistor u₁₁. The gate contact and the source contact of thetransistor u₁₂ are connected to each other, and to the source contact ofthe transistor u₁₄. The transistor u₁₄ is connected at the drain contactto the signal line for the voltage V_(L) and at the gate contact to thesignal line for the clock signal φ_(A).

Transistors MOS u₂₂, u₂₂, u₂₃, and u₂₄ make up the same circuit as thatmade up of the transistors MOS u₁₁, u₁₂, u₁₃, and u₁₄. The drain contact(output point) of the transistor u₁₂ is connected to the gate contact(input point) of the transistor u₂₂. However, the connection of thesignals φ_(A) and φ_(B) thereto is inverted. The bit input correspondsto the gate contact of the gate contact of the transistor u₁₁. The bitoutput corresponds to the drain contact of the transistor u₂₂. An n-bitshift register is formed by connecting the inputs and outputs of thosebit cells in a cascade fashion. A start pulse φ_(s) is inputted to theleast significant bit cell through an analog switch u₀₀ which isrendered conductive in synchronism with the clock signal φ_(A).

The third drive circuit 12 includes a shift register for producing drivesignals S_(l) to S_(n) at predetermined times, as described above.

The scan read operation will be described in detail with reference toFIG. 18. The period T_(VB) corresponds to the vertical blanking period,the period T_(HB) corresponds to the horizontal blanking period, periodT_(1H) corresponds to the horizontal scan period. Further, "H" indicates12 V, "M" indicates 0 V, "L" indicates -8 V, and "HH" is approximately12 V, which is equal to the substrate voltage.

During the period T_(VB), the timing signal φ_(H) goes high (H) at apredetermined time t2, and is at the "M" level during the remainingtime. The timing signal φ_(G) is always at the "M" level. The timingsignal φ_(FS) goes high (H) as the timing signal φ_(H) goes high, and iskept at the "L" level during the remaining time. The drive signals S_(l)to S_(n) generated from the third drive circuit 12 are always in "L"level. During the period T_(VB), all of the NMOS transistors of thefirst drive circuit 10 are rendered conductive by the timing signalφ_(G) at the "M" level, while all of the drive signals S_(l) to S_(n) ofthe third drive circuit 12 are set to the "L" level. Accordingly, all ofthe NMOS transistors in the second drive circuit 11 become conductive.All of the gate electrodes G₁₁, G₂₁, G₃₁, G₄₁ to G_(1n), G_(2n), G_(4n)are controlled by the first drive circuit 10.

More specifically, when the timing signals φ_(H) and φ_(FS) are not atthe "H" level, the gate signals φ₁₁, φ₃₁, φ₁₂, φ₃₂ to φ_(1n), φ_(3n),which are applied to the odd-numbered gate electrodes G₁₁, G₃₁, G₁₂, G₃₂to G_(1n), G_(3n), are each equal in voltage level to the signal V_(L)(constantly set at -8 V). Under this condition, potential barriers aregenerated in the vertical charge transfer paths L_(l) to L_(m) underthose gate electrodes.

The gate signals φ₂₁, φ₄₁, φ₂₂, φ₄₂ to φ_(2n), φ_(4n), which are appliedto the even-numbered gate electrodes G₂₁, G₄₁, G₂₂, G₄₂ to G_(2n),G_(4n), are each equal in voltage to the signal φ_(H) at the "M" level.Under this condition, transfer pixels are generated in the verticalcharge transfer paths L_(l) to L_(m) under those gate electrodes.

Accordingly, all of the portions adjacent to the transfer gates Tg (seeFIG. 14) serve as the transfer pixels being separated from one anotherby the potential barriers.

Under this condition, when the timing signals φ_(H) and φ_(FS) go highat time t2, all of the npn transistors Q₂₁, Q₄₁, Q₆₁, . . . becomeconductive, and the "H" level voltage of approximately 15 to 25 V isapplied to only the even-numbered gate electrodes G₂₁, G₄₁, G₂₂, G₄₂ toG_(2n), G_(4n). Accordingly, all of the transfer gates Tg becomeconductive, and all of the pixel signals of all of the photodiodes aretransferred to the adjacent transfer pixels.

During the period T_(VB), a so-called field shift operation isperformed, so that as at time t₁ in FIG. 22, the pixel signals (markedas shaded squares) are transferred to the vertical charge transferpaths. During the period T_(HB) corresponding to the first horizontalblanking period, the timing signal φ_(G) is always in "L" level.Accordingly, all of the NMOS transistors in the first drive circuit 10become nonconductive and are separated from all of the gate electrodes.

Only the drive signal S₁ at the first output terminal of the third drivecircuit 12 is set at the "M" level, while the remaining drive signals S₂to S_(n), are at the "L" level. This renders conductive only the firstset of NMOS transistors m₁₁, m₂₁, m₃₁, m₄₁ concerning the drive signalS₁ of the second drive circuit 11.

During the period that only the drive signal S₁ is set to "M" level, thetiming signals φ₁, φ₂, φ₃, and φ₄ of four phases for the vertical chargetransfer are inputted to the second drive circuit 11. Accordingly, onlythe first set of first to fourth gate signals S₁₁, S₂₁, S₃₁, and S₄₁ areequal in level to the timing signals φ₁, φ₂, φ₃, and φ₄. The chargetransfer is performed by the first set of first to fourth gateelectrodes G₁₁, G₂₁, G₃₁, and G₄₁. The enlarged signal waveforms duringthe period T_(HB) are shown in FIG. 19.

As a consequence, the signal charges are transferred to the horizontalcharge transfer path 8 at the times (indicated by numerals 1, 2, 3, 4,5, 6, and 7) of the gate signals φ₁₁, φ₂₁, φ₃₁, and φ₄₁ in FIG. 19, asin the first transfer shown in FIG. 22. A pixel signal q_(1j) of thefirst line closest to the horizontal charge transfer path 8 istransferred to the transfer path 8. A pixel signal q_(2j) of the secondline moves to the first line position.

Then, during the first horizontal scan period T_(1H) (between times t₄and t₅), the variation of the signal applied to each gate electrodestops, and the horizontal charge transfer path 8 vertically transferssignal charges in synchronism with the gate signals α₁ to α₄ recurringat predetermined times according to the four-phase drive system. As aresult, pixel signals of the first one line are read out.

During a period between times t₅ to t₇, a sequence of operations, whichis similar to that during the period between times t₃ to t₅, is repeatedto read the pixel signals of the next line out of the image pick-updevice. During the horizontal blanking period T_(HB) between times t₃ tot₄, the drive signals S₁ and S₂ of the third drive circuit 12 aresimultaneously set to "M" level, and the remaining drive signals S₃ toS_(n) are set to "L" level. The enlarged signal waveforms during thisperiod T_(HB) are shown in FIG. 20.

As a result, a set of the first to fourth gate electrodes G₁₁ to G₄₁,and two sets of fifth to eighth G₁₂ to G₄₂ are driven by the gatesignals φ₁₁ to φ₄₁ and φ₁₂ to φ₄₂, which are equal to the timing signalsφ₁, φ₂, φ₃, and φ₄. The result is the vertical transfer of the pixelsignals under those gate electrodes.

The timing chart shown in FIG. 20 shows that as indicated by the secondvertical scan in FIG. 22, the pixel signal q_(2j) of the second line istransferred to the horizontal charge transfer path 8. Two lines of thepixel signals q_(3j) of the third line and the pixel signal q_(4j) ofthe fourth line are transferred to the horizontal charge transfer path8.

During the horizontal scan period T_(1H) between times t₆ and t₇, thehorizontal charge transfer path 8 reads out the pixel signal q_(2j) ofthe second line.

The third scan read starts at time t₇. Then, the drive signals S₁, S₂,and S₃ are set to "M" level, while the remaining drive signals S₄ toS_(n) of the third drive circuit 12 are set to "L" level. The first tothird sets of first to 12th gate electrodes G₁₁ to G₄₁, G₁₂ to G₄₂ toG₄₂, and G₁₃ to G₄₂ are driven for the vertical charge transfer.Accordingly, as in the third transfer of FIG. 22, the pixel signalq_(3j) of the third line is transferred to the horizontal chargetransfer path 8. The pixel signals q_(4j) to q_(5j) of the 4th to 7thlines are transferred every two lines to the horizontal charge transferpath 8. The pixel signal q_(6j) of one line is transferred to there.

Then, the pixel signal q_(3j) is read out of the photodiodes by thehorizontal charge transfer path 8.

Subsequently, the drive signals S₄ to S_(n) of the third drive circuit12 are progressively inverted to the "M" level every time the pixelsignal of each line is read out. The gate electrodes to be driven areincreased every four gate electrodes. During the horizontal blankingperiod T_(HB) (between times t₉ and t₁₀), all of the gate signals φ₁₁ toφ_(4n) have the same waveforms as those of the timing signals φ₁ to φ₄,as shown in FIG. 21. The pixel signals of the last line are read out bythe final scan read operation.

FIG. 23 shows the K-th and (K+1)th vertical charge transfer operations,for example, in terms of potential profiles. As shown, in order from thetransfer pixel closest to the horizontal charge transfer path 8, theintervals of the idle transfer pixels progressively increase. With this,the pixel signals are progressively read out in the order from the pixelsignal closest to the transfer path 8 to the succeeding ones.

Thus, in the still picture photographing mode, all of the pixel signalscan be generated by one-time frame scan read, and the pixel signals maybe scan read without mixing them. Accordingly, the image pick-up deviceof the embodiment can reproduce a still picture at a high resolution,which is free from flicker, pseudocolor and the like.

The operation of the image pick-up device when it is in the motionpicture photographing mode will be described. In this mode, theodd-numbered field and the even-numbered field, which are shifted by oneline one from the other, are field scan read, to complete the interlacescan read.

The basic times of scan reading the respective fields are substantiallythe same as those shown in FIGS. 17 and 18 except the signal timesduring the period T_(HB) corresponding to the horizontal blankingperiod.

For the scan read of the odd-numbered field, the times during the periodfrom t₃ to t₄ in FIG. 18 is replaced by the times shown in FIG. 25, thetimes during the period from t₅ to t₆ in FIG. 18 are replaced by thetimes shown in FIG. 26, and the times during the period from t₉ to t₁₀in FIG. 18 are replaced by the times shown in FIG. 27. The times duringthe horizontal scan period T_(1H) remains unchanged.

For the scan read of the even-numbered field, the times during theperiod from t₃ to t₄ in FIG. 18 are replaced by the times shown in FIG.28, the times during the period from t₅ to t₆ in FIG. 18 are replaced bythe times shown in FIG. 29, and the times during the period from t₉ tot₁₀ in FIG. 18 are replaced by the times shown in FIG. 30. The timesduring the horizontal scan period T_(1H) remains unchanged.

To start the scan read of the odd-numbered field, the exposure is set upand continued, and during the vertical blanking period T_(VB), the pixelsignals of all of the photodiodes are shifted to the transfer pixelsunder the even-numbered gate electrodes G₂₁, G₄₁, G₂₂, G₄₂, . . . ,G_(2n), G_(4n) of the vertical charge transfer paths L₁ to L_(m).

Then, during the first horizontal blanking period (see FIG. 25), thefirst and second drive signals S₁ and S₂ of the third drive circuit 12vary over two periods as shown. The timing signals φ₁, φ₂, φ₃, and φ₄ ofthe second drive circuit 11 are supplied two times for each period.Accordingly, during the first period of the period from t₃ to t₄, thegate signals φ₁₁ to φ₄₁ are applied to only the first set of gateelectrodes G₁₁ to G₄₁. During the next period, the gate signals φ₁₁ toφ₄₁ and φ₁₂ to φ₄₂ are respectively applied to the first set of gateelectrodes G₁₁ to G₄₁ and the second set of gate electrodes G₁₂ to G₄₂.

As shown in FIG. 25, the pixel signals of the transfer pixels under thefirst set of the gate electrodes G₂₁ and the pixel signals of thetransfer pixels under the second set of the gate electrodes G₂₂ areshifted to the transfer pixels of the horizontal charge transfer path 8where those pixel signals are mixed.

During the first horizontal scan period T_(1H), the horizontal chargetransfer path 8 horizontally scans to time sequentially output the mixedpixel signals.

Then, during the second horizontal blanking period (see FIG. 26), thefirst to fourth drive signals S₁ to S₄ from the third drive circuit 12vary over the two periods as shown. As a result, the pixel signals underthe third and fourth gate electrodes G₁₃ to G₄₃ and G₁₄ to G₄₄ aretransferred to and mixed in the horizontal charge transfer path 8.

During the next horizontal scan period T_(1H), the horizontal chargetransfer path 8 horizontally scans to time sequentially output the mixedpixel signals of the second line.

The above sequence of operations is repeated during the respectivehorizontal blanking periods and horizontal scan periods, so that thedrive signals S_(l) to S_(n) from the third drive circuit 12 aregenerated progressively expanding. As in the above case, the horizontalcharge transfer path 8 outputs all of the pixel signals while mixingthem.

FIG. 27 shows times of reading out the pixel signals of the last line.

FIG. 31 is a diagram of potential profiles showing charge transferoperations by the first to sixth gate electrodes during the firsthorizontal blanking period T_(HB) (times t₃ to t₄). At times 0 to 8 and0 to 6, the potential variations with respect time are profiled asshown.

The scan read of the even-numbered field will be described. To start,the exposure is set up and continued, and during the vertical blankingperiod T_(VB) in FIG. 18, the pixel signals of all of the photodiodesare shifted to the transfer pixels under the even-numbered gateelectrodes G₂₁, G₄₁, G₂₂, G₄₂, G_(2n), G_(4n) of the vertical chargetransfer paths L_(l) to L_(m).

Then, during the first horizontal blanking period (see FIG. 28), thefirst drive signal S₁ of the third drive circuit 12 vary over twoperiods as shown. The timing signals φ₁, φ₂, φ₃, and φ₄ of the seconddrive circuit 11 are supplied for the later period. Accordingly, duringthe period from t₃ to t₄, the gate signals φ₁₁ to φ₄₁ are applied toonly the gate electrodes G₁₁ to G₄₁.

As shown in FIG. 28, the pixel signals of the transfer pixels under thefirst set of the gate electrodes G₂₁ are shifted to the transfer pixelsof the horizontal charge transfer path 8. During the first horizontalscan period T_(1H), the horizontal charge transfer path 8 horizontallyscans to time sequentially output the mixed pixel signals. The signalsread out by the first scan read are discharged as unnecessary signals.

Then, during the second horizontal blanking period (see FIG. 29), thefirst to third drive signals S₁ to S₃ from the third drive circuit 12vary over the two periods as shown. As a result, the pixel signals underthe first and second gate electrodes G₃₁ to G₄₁ and G₁₂ to G₄₂ aretransferred to and mixed in the horizontal charge transfer path 8. Thepixel signals under the third set of gate electrodes G₁₃ to G₂₃ aretransferred to under the first set of gate electrodes.

During the next horizontal scan period T_(1H), the horizontal chargetransfer path 8 horizontally scans to time sequentially output the mixedpixel signals of the second line.

The above sequence of operations is repeated during the respectivehorizontal blanking periods and horizontal scan periods, so that thedrive signals S_(l) to S_(n) from the third drive circuit 12 aregenerated progressively expanding. As in the above case, the horizontalcharge transfer path 8 outputs all of the pixel signals while mixingthem.

FIG. 30 shows times of reading out the pixel signals of the last line.

FIG. 32 is a diagram of potential profiles showing charge transferoperations by the first to sixth gate electrodes during the firsthorizontal blanking period T_(HB) (times t₅ to t₆) in FIG. 29. At times0 to 8 and 0 to 6, the potential variations with respect time areprofiled as shown.

As seen from FIGS. 31 and 32, in the motion picture photographing modeas mentioned above, the mixing and combination of the pixel signals inthe odd-numbered field are shifted by one line from those in theeven-numbered field. Therefore, the interlace scan read is realized.

Another embodiment of a solid-state image pick-up device of the CCD typewill be described. The structure of the image pick-up device isillustrated in FIG. 33 corresponding to FIG. 14. The differences betweenthe FIG. 33 structure and the FIG. 14 structure is primarily that npntransistors Q₄₁, Q₄₂, Q₄₃ . . . are controlled by the first field shiftsignal φ_(FSA), and npn transistors Q₂₁, Q₂₂, Q₂₃, . . . by the secondshift signal φ_(FSB). Those shift signals φ_(FSA) and φ_(FSB) aregenerated by the sync control circuit 6. The remaining structure of thesecond embodiment resembles that shown in FIGS. 13-16 and 23. When theimage pick-up device is applied to a camera, for example, the structureis substantially the same as that of FIG. 12.

The still picture photographing mode proceeds at the same times as thosein FIGS. 17 through 21 with some exceptions.

The shift signal φ_(FSA) and φ_(FSB) shown in FIG. 33 are substituted bythe signal φ_(FS). All of the transistors Q₂₁, Q₄₁, Q₂₂, Q₄₂, Q₂₃, Q₄₃ .. . in FIG. 33 are controlled by the signal φ_(FS). The operation of thestill picture photographing mode proceeds is equal to that of the firstembodiment. The transfer of the pixel signals is performed as shown inFIGS. 22 and 23, realizing the noninterlace/full frame scan read.

In the motion picture photographing mode, all of the output signalsS_(l) to S_(n) of the third drive circuit 12 are set to "M" level, andall of the transistors m₁₁, m₂₁, m₃₁, m₄₁ to m_(1n), m_(2n), m_(3n),m_(4n) are made conductive. In the scan read mode of the odd-numberedfield, the first field shift signal φ_(FSA) is set to "H" level, and thesecond shift signal φ_(FSB) is set to "L". Under this condition, theodd-numbered field is shifted to scan read pixel signals according tothe four-phase drive system of the timing signals φ₁, φ₂, φ₃, and φ₄. Inthe scan read mode of the even-numbered field, the first field shiftsignal φ_(FSA) is set to "L" level, and the second shift signal φ_(FSB)is set to "H". Under this condition, the odd-numbered field is shiftedto scan read pixel signals according to the four-phase drive system ofthe timing signals φ₁, φ₂, φ₃, and φ₄. In this way, the motion pictureis photographed in the interlace scan read mode.

Still another embodiment of a solid-state image pick-up device of theCCD type will be described. The structure of the image pick-up deviceshown in FIGS. 13, 14 and 23 is available for that of the image pick-updevice of this embodiment. The still picture photographing mode is equalto that of the first embodiment.

The operation of the picture photographing mode will described. Thetimes of the respective signals are similar to those in FIG. 18, but thetimes of the vertical blanking period T_(VB) shown in FIG. 18 arereplaced by the times shown in FIG. 34 in the scan read mode for theodd-numbered field, and the times shown in FIG. 35 in the scan read modefor the even-numbered field.

In the scan read mode for the odd-numbered field, during the verticalblanking period T_(VB), as shown in FIG. 18, the field shift signalφ_(FSA) is set to "H" level, so that the pixel signals corresponding toall of the pixels are transferred to the transfer pixels under theeven-numbered gate electrodes of each set. Then, the signal φ_(G) is setto "L" level, and all of the output signals S_(l) to S_(n) of the thirddrive circuit 12 are set to "M" level, to render all of the transistorsm₁₁, m₂₁, m₃₁, m₄₁ to m_(1n), m_(2n), m_(3n), m_(4n) conductive. Underthis condition, at times 0, 1, 2, 3, 0 the gate signals φ₁₁ to φ_(4n)corresponding to the timing signals φ₁, φ₂, φ₃, and φ₄ are applied tothe gate electrodes G₁₁ to G_(4n). Then, according to the potentialprofile as shown in FIG. 36, a pair of pixel signals are mixed andretained in the transfer pixels the second gate electrodes of each set.The transfer pixels under the fourth gate electrodes of each set areempty.

The scan read is applied at the times (see FIG. 8) similar to those inthe still picture photographing mode of the first embodiment, thereby toperform the scan read for the odd-numbered field.

In the scan read mode for the even-numbered field, during the verticalblanking period T_(VB), as shown in FIG. 35, the field shift signalφ_(FS) is set to "H" level, so that the pixel signals corresponding toall of the pixels are transferred to the transfer pixels under theeven-numbered gate electrodes of each set. Then, the signal φ_(G) is setat the "L" level, and all of the output signals S_(l) to S_(n) of thethird drive circuit 12 are set to "M" level, to render all of thetransistors m₁₁, m₂₁, m₃₁, m₄₁ to m_(1n), m_(2n), m_(3n), m_(4n)conductive. Under this condition, at times 0, 1, 2, 3, 0 the gatesignals φ₁₁ to φ_(4n) corresponding to the timing signals φ₁, φ₂, φ₃,and φ₄ are applied to the gate electrodes G₁₁ to G_(4n). Then, accordingto the potential profile as shown in FIG. 37, a pair of pixel signalsare mixed and retained in the transfer pixels under the second gateelectrodes of each set. The transfer pixels under the fourth gateelectrodes of each set are empty. Here, in the even-numbered field, thecombinations of the mixed pixel signals in the even-numbered field areshifted by one line.

The scan read is applied at the times (see FIG. 8) similar to those inthe still picture photographing mode of the first embodiment, thereby toperform the scan read for the even-numbered field.

Thus, in the motion picture photographing mode of the third embodiment,the pixel signals are mixed in the transfer pixels of the verticalcharge transfer paths L_(l) to L_(m), and the 2 field scan read isapplied to realize the interlace scan read.

Those embodiments thus far described, in the still picture photographingmode, can provide a clear image by the noninterlace scan read. Themotion picture photographing mode can also be performed by the interlacescan read. Further, the image pick-up devices are inventive in thestructure and the drive system.

As described above, the present invention successfully provides asolid-state CCD image pick-up device, which is operable in either of twoscan read modes, an interlace scan read mode for photographing a motionpicture and a noninterlace/frame scan read mode for photographing astill picture.

In another embodiment of the present invention, the third drive circuit12 will be described with reference to FIGS. 38 to 40. The third drivecircuit 12 consists of a shift register for shifting a start pulse φ_(S)in synchronism with two-phase timing signal φ_(A) and φ_(B) tosequentially generate drive signals of logic "H" in the order from thelow- order bit to the high-order bit. In the first period, only thefirst drive signal S₁ goes high ("H"), while the remaining high-orderbits are all low ("L") in logic level. In the second period, twolow-order bits S₁ and S₂ go high, while the remaining high-order bitsare low. In the third period, three low-order bits S₁, S₂, and S₃ gohigh, while the remaining high-order bits are low. Thus, the number ofhigh drive signals progressively increases in order from the low-orderbits to the high-order bits.

As shown in FIG. 38, each bit has a cell structure, and hence thecircuit of the first bit will be typically described. The source-drainpaths of three MOS u₁₁, u₁₂, u₁₃, and u₁₄ are connected in seriesbetween a signal line of the voltage V_(L) and a signal line of theclock signal φ_(B). A signal line for the reset signal RS is connectedto the gate contact of the transistor u₁₃. A bootstrap capacitor ε₁₁ isconnected between the gate contact and the source contact of thetransistor u₁₁. The gate contact and the drain contact of the transistoru₁₂ are connected to each other, and to the drain contact of thetransistor u₁₄. The transistor u₁₄ is connected at the drain contact tothe signal line for the voltage V_(L) and at the gate contact to thesignal line for the timing signal φ_(A).

Transistors MOS u₂₂, u₂₂, u₂₃, and u₂₄ make up the same circuit as thatmade up of the transistors MOS u₁₁, u₁₂, u₁₃, and u₁₄. The drain contact(output point) of the transistor u₁₂ is connected to the gate contact(input point) of the transistor u₂₂. However, the connection of thesignals φ_(A) and φ_(B) thereto is inverted.

The bit input corresponding to the gate contact of the gate contact ofthe transistor u₁₁. The bit output corresponding to the source contactof the transistor u₂₂. An n-bit shift register is formed by connectingthe inputs and outputs of those bit cells in a cascade fashion. A startpulse φ_(S) is inputted to the least significant bit cell through ananalog switch u₀₀ which is rendered conductive in synchronism with theclock signal φ_(A).

The shift register thus arranged will operate in the following. As shownin FIG. 39, during a period between t₀ to t_(n), when the start pulseφ_(S) is set to "H" level, the bit output signals are successively setto "H" level from the low-order bit output signal S1 to the mostsignificant bit output signal Sn. If a reset signal φ_(RS) is set to "H"level at a desired timing, then the bit output signals S1 to Sn are allreset to "L" level. Signals appearing at contacts i₁ to i₉ in theinternal circuits forming bits shown in FIG. 38 take waveforms as shownin FIG. 40. As shown, the voltages at the gate contacts i₁, i₃, i₇, i₉,. . . of the transistors u₁₁, u₂₁, . . . are raised through thefunctions of the bootstrap capacitors ε₁₁, ε₁₂, . . . . Therefore, thosevoltages of satisfactory amplitudes are wave shaped to form rectangularbit output signals Sl to Sn.

The operation of the CCD image pick-up device thus constructed will bedescribed using an electronic still camera for photographing a stillpicture into which the image pick-up device is incorporated.

The operation of the image pick-up device when it takes a still picturewill be described with reference to FIG. 18. It is assumed that theperiod T_(VB) corresponds to the vertical blanking period of a standardtelevision system. At a predetermined time during the period T_(VB), aso-called field shift to shift the pixel charges from the photodiodes tothe vertical charge transfer paths is performed. The electronic shutterfunction is realized if the time for the field shift operation is madeto correspond to a time of closing a shutter (time of an exposurecompletion). Accordingly, the exposure operation starts at a time afterthe shutter close time, and the device is so controlled that theexposure time ranges from the exposure start time to a time of startingthe field shift operation.

The excessive charges possibly causing the smear component and the darkcurrent component in the vertical charge transfer paths L_(l) to L_(m)and the horizontal charge transfer path 8, are discharged by the chargetransfer operation before the field shift starts. Further, immediatelybefore the exposure starts, the unnecessary charges in the photodiodeshave been drained by the vertical overflow drain structure.

During the period T_(VB) corresponding to the vertical blanking period,the pixel signals of all of the photodiodes are simultaneouslytransferred to the transfer pixels of the vertical charge transfer pathsL_(l) to L_(m). During the period T_(HB) corresponding to the horizontalblanking period, a pixel signal of the transfer pixel closest to thehorizontal charge transfer path 8 is transferred to the transfer path 8.During a period T_(1H) corresponding to the horizontal scan period(called a 1 H period), the pixel signals of one line are horizontallytransferred through the horizontal charge transfer path 8. As a result,the pixel signals of the first line are read out.

Then, during the period T_(HB) corresponding to the next horizontalblanking period, the vertical charge transfer paths L_(l) to L_(m) feedthe pixel signals of the next line to the horizontal charge transferpath 8. During a period T_(1H) corresponding to the next horizontal scanperiod, the pixel signals are horizontally transferred through thehorizontal charge transfer path 8. In this way, the pixel signals of thesecond line are read out.

The pixel signals of the third line are likewise read out of thephotodiodes by using periods T_(HB) and T_(1H). The pixel signals of theremaining lines are successively read out while repeating a similarsequence of operations. Finally, all of the pixel signals of one frameare read out.

The scan read operation will be described in detail with reference toFIG. 18 showing a timing chart of drive signals and timing signals. Inthe figure, the period T_(VB) corresponds to the vertical blankingperiod, the period T_(HB) corresponds to the horizontal blanking period,period T_(1H) corresponds to the horizontal scan period. Further, "H"indicates 12 V, "M" indicates 0 V, "L" indicates -8 V, and "HH"indicates approximately 15 to 25 V equal to the substrate voltage.

During the period T_(VB) corresponding to the vertical blanking period,the timing signal φ_(H) and φ_(G) go high (H) only at a predeterminedtime t2, while remains "M" in level at the remaining times. The timingsignal φ_(G) is always at the "M" level. The timing signal φ_(FS) goeshigh (H) as the timing signal φ_(H) goes high, while being kept at the"L" level during the remaining times. The drive signals S₁ to S_(n)generated from the third drive circuit 12 are always at the "L" level.

During the period T_(VB), all of the NMOS transistors of the first drivecircuit 10 are rendered conductive by the timing signal φ_(G) of "H" and"M" level, while at the same time all of the drive signals S_(l) toS_(n) of the third drive circuit 12 are placed at the "L" level.Accordingly, all of the NMOS transistors in the second drive circuit 11become conductive. All of the gate electrodes G₁₁, G₂₁, G₃₁, G₄₁ toG_(1n), G_(2n), G_(4n) are controlled by the first drive circuit 10.

More specifically, when the timing signals φ_(H) and φ_(FS) are not atthe "H" level, the gate signals φ₁₁, φ₃₁, φ₁₂, φ₃₂ to φ_(1n), φ_(3n),which are applied to the odd-numbered gate electrodes G₁₁, G₃₁, G₁₂, G₃₂to G_(1n), G_(3n), are each equal in voltage level to the signal V_(L)(constantly set at -8 V). Under this condition, potential barriers aregenerated in the vertical charge transfer paths L_(l) to L_(m) underthose gate electrodes.

The gate signals φ₂₁, φ₄₁, φ₂₂, φ₄₂ to φ_(2n), φ_(4n), which are appliedto the even-numbered gate electrodes G₂₁, G₄₁, G₂₂, G₄₂ to G_(2n),G_(4n), are each equal in voltage to the signal φ_(H) at the "M" level.Under this condition, transfer pixels are generated in the verticalcharge transfer paths L_(l) to L_(m) under those gate electrodes.

Accordingly, all of the portions adjacent to the transfer gates Tg (seeFIG. 14) serve as the transfer pixels being separated from one anotherby the potential barriers.

Under this condition, when the timing signals φ_(H) and φ_(FS) go highat time t2, all of the npn transistors Q₂₁, Q₄₁, Q₆₁, . . . becomeconductive, and the "H" level voltage of approximately 12 V is appliedto only the even-numbered gate electrodes G₂₁, G₄₁, G₂₂, G₄₂ to G_(2n),G_(4n). Accordingly, all of the transfer gates Tg become conductive, andall of the pixel signals of all of the photodiodes are transferred tothe adjacent transfer pixels.

As already described referring to FIG. 17, the exposure process has beencompleted just before the time t₂, and the removal of the unnecessarycharges has also been completed. During the period T_(VB), a so-calledfield shift operation is performed, so that as at the time t₁ shown inFIG. 22, the pixel signals (shaded squares) are transferred to thevertical charge transfer paths. During the period T_(HB) correspondingto the first horizontal blanking period, the timing signal φ_(G) isalways at the "L" level. Accordingly, all of the NMOS transistors in thefirst drive circuit 10 become nonconductive and are separated from allof the gate electrodes.

Only the drive signal S₁ at the first output terminal of the third drivecircuit 12 is placed at the "M" level, while the remaining drive signalsS₂ to S_(n) are at the "L" level. This renders conductive only the firstset of NMOS transistors m₁₁, m₂₁, m₃₁, m₄₁ concerning the drive signalS₁ of the second drive circuit 11.

During the period that only the drive signal S₁ is set to "M" level, thetiming signals φ₁, φ₂, φ₃, and φ₄ of four phases for the vertical chargetransfer are inputted to the second drive circuit 11. Accordingly, onlythe first set of first to fourth gate signals φ₁₁, φ₂₁, φ₃₁, and φ₄₁ areequal in level to the timing signals φ₁, φ₂, φ₃, and φ₄. The chargetransfer is performed by the first set of first to fourth gateelectrodes G₁₁, G₂₁, G₃₁, and G₄₁. The enlarged signal waveforms duringthe period T_(HB) are shown in FIG. 19.

As a consequence, the signal charges are transferred to the horizontalcharge transfer path 8 at the times (indicated by numerals 1, 2, 3, 4,5, 6, and 7) of the gate signals φ₁₁, φ₂₁, φ₃₁, and φ₄₁ in FIG. 19, asin the first transfer shown in FIG. 22. A pixel signal q_(1j) of thefirst line closest to the horizontal charge transfer path 8 istransferred to the transfer path 8. A pixel signal q_(2j) of the secondline moves to the first line position.

Then, during the first horizontal scan period T_(1H) (between times t₄and t₅), the variation of the signal applied to each gate electrodestops, and the horizontal charge transfer path 8 vertically transferssignal charges in synchronism with the gate signals α₁ to α₄ recurringat predetermined times according to the four- or two-phase drive system.As a result, pixel signals of the first one line are read out.

During a period between times t₅ to t₇, a sequence of operations, whichis similar to that during the period between times t₃ to t₅, is repeatedto read the pixel signals of the next line out of the image pick-updevice. During the horizontal blanking period T_(HB) between times t₃ tot₄, the drive signals S₁ and S₂ of the third drive circuit 12 aresimultaneously set to "M" level, and the remaining drive signals S₃ toS_(n) are set to "L" level. The enlarged signal waveforms during thisperiod T_(HB) are shown in FIG. 20.

Consequently, a set of the first to fourth gate electrodes G₁₁ to G₄₁,and two sets of fifth to eighth G₁₂ to G₄₂ are driven by the gatesignals φ₁₁ to φ₄₁ and φ₁₂ to φ₄₂, which are equal to the timing signalsφ₁, φ₂, φ₃, and φ₄. The result is the vertical transfer of the pixelsignals under those gate electrodes.

The timing chart shown in FIG. 20 shows that as indicated by the secondvertical scan in FIG. 22, the pixel signal q_(2j) of the second line istransferred to the horizontal charge transfer path 8. Two lines of thepixel signals q_(j3) of the third line and one line of the pixel signalq_(j4) of the fourth line are transferred to the horizontal chargetransfer path 8.

During the horizontal scan period T_(1H) between times t₆ and t₇, thehorizontal charge transfer path 8 reads out the pixel signal q_(2j) ofthe second line.

The third scan read starts at time t₇. Then, the drive signals S₁, S₂,and S₃ are set to "M" level, while the remaining drive signals S₄ toS_(n) of the third drive circuit 12 are set to "L" level. The first tothird sets of first to 12th gate electrodes G₁₁ to G₄₁, G₁₂ to G₄₂ toG₄₂, and G₁₃ to G₄₂ are driven for the vertical charge transfer.Accordingly, as in the third transfer of FIG. 22, the pixel signalq_(3j) of the third line is transferred to the horizontal chargetransfer path 8. The pixel signals q_(4j) to q_(7j) of the 4th to 7thlines are transferred every line to the horizontal charge transfer path8.

Then, the pixel signal q_(3J) is read out of the photodiodes by thehorizontal charge transfer path 8.

Subsequently, the drive signals S₄ to S_(n) of the third drive circuit12 are progressively inverted to "M" level every time the pixel signalof each line is read out. The gate electrodes to be driven are increasedevery four transfer pixels under the gate electrodes. During thehorizontal blanking period T_(HB) (between times t₉ and t₁₀), all of thegate signals φ₁₁ to φ_(4n) have the same waveforms as those of thetiming signals φ₁ to φ₄, as shown FIG. 21. The pixel signals of the lastline are read out by the final scan read operation.

FIG. 23 shows the K-th and (K+1)th vertical charge transfer operations,for example, in terms of potential profiles. As shown, in order from thetransfer pixel closest to the horizontal charge transfer path 8, theintervals of the idle transfer pixels progressively increase. With this,the pixel signals are read out in the order from the pixel signals ofthe pixel closed to the transfer path 8 to the succeeding ones.

Thus, in the present embodiment, the pixel signals of one frame can beread out by one-time frame scan read operation.

Also in the embodiment, the width of the odd-numbered gate electrodes iswider than that of the even-numbered gate electrodes. This feature allowincrease of a charge retaining capacitance of the transfer pixelsadjacent to the transfer gates. Additionally, during the vertical chargetransfer, the transfer pixels under the even-numbered gate electrodesare, of necessity, used for the charge transfer, thereby improving thecharge transfer efficiency.

The shift register corresponding to the third drive circuit produces therespective bit output signals at the frequency equal to that of thetiming signal. Therefore, there is no need for increasing the frequencyof the timing signal, although the prior shift register needs theincrease of it. Further, the shift register can be reset at a desiredtiming. In the embodiment, the charge transfer is performed insynchronism with the four-phase timing signals φ₁, φ₂, φ₃, and φ₄ duringthe period T_(HB) corresponding to each horizontal blanking period. Ifnecessary, the timing signals of 4 or more phases may be used fordriving the gate electrodes corresponding to the number of phases.

The solid-state image pick-up device having the thus constructed shiftregister operates in synchronism with the timing signal in a manner thatthe number of the bit output signals of "H" level gradually increases inthe order from the low-order bit to the high-order bit. That is, duringa first period, only the first bit output signal is at the "H" level,while the remaining high-order bits are all at the "L" level. During thenext period, the bit output signals at the two low-order bits are at the"H" level, while the remaining high-order bits are at the "L" level.During the succeeding period, the bit output signals at the threelow-order bits are at the "H" level, while the remaining high-order bitsare at the "L" level.

The bit output signals vary in synchronism with the frequency of thetiming signal. Additionally, the shift register can be reset at any timeby a reset signal.

Other modifications and variations to the invention will be apparent tothose skilled in the art from the foregoing disclosure and teachings.Thus, while only certain embodiments of the invention have beenspecifically described herein, it will be apparent that numerousmodifications may be made thereto without departing from the spirit andscope of the invention.

What is claimed is:
 1. A solid-state image pick-up device of the CCDtype, said device comprising:a n-type semiconductor substrate; avertical overflow drain structure for draining excessive charges in aphotodetecting area into said semiconductor substrate; a first p-typewell layer buried in said semiconductor substrate; said photodetectingregion comprising a plurality of charge transfer paths formed in saidfirst p-type well layer; a second p-type well layer, formed separatelyfrom said first p-type well layer, and buried in said semiconductorsubstrate; and a first drive circuit formed in said second p-type welllayer, and a second drive circuit formed in said second p-type welllayer, wherein each of said first and second drive circuits comprises aplurality of transistors, and wherein, within each of said drivecircuits, said plurality of transistors have the same structure.
 2. Asolid-state image pick-up device as claimed in claim 1, wherein saidsecond p-type well layer comprises two p-type well regions, said firstdrive circuit being formed in one of said p-type well regions, and saidsecond drive circuit being formed in the other of said p-type wellregions.